Logo link to homepage

Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.


Recently Published Bulletin Reports

Krakatau (Indonesia) Tephra and steam explosions in the crater lake; explosions in December 2019 build a tephra cone

Mayotte (France) Seismicity and deformation, with submarine E-flank volcanism starting in July 2018

Fernandina (Ecuador) Fissure eruption produced lava flows during 12-13 January 2020

Masaya (Nicaragua) Lava lake persists with lower temperatures during August 2019-January 2020

Reventador (Ecuador) Nearly daily ash emissions and frequent incandescent block avalanches August 2019-January 2020

Pacaya (Guatemala) Continuous explosions, small cone, and lava flows during August 2019-January 2020

Kikai (Japan) Single explosion with steam and minor ash, 2 November 2019

Nevado del Ruiz (Colombia) Intermittent ash, gas-and-steam, and SO2 plumes, and thermal anomalies during January 2018-December 2019

Erebus (Antarctica) Lava lakes persist through 2019

Sangay (Ecuador) Continuing ash emissions, lava flows, pyroclastic flows, and lahars through December 2019

Shishaldin (United States) Multiple lava flows, pyroclastic flows, lahars, and ashfall events during October 2019 through January 2020

Sangeang Api (Indonesia) Ash emissions and lava flow extrusion continue during May 2019 through January 2020



Krakatau (Indonesia) — February 2020 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


Tephra and steam explosions in the crater lake; explosions in December 2019 build a tephra cone

Krakatau volcano in the Sunda Strait between Indonesia’s Java and Sumatra Islands experienced a major caldera collapse around 535 CE; it formed a 7-km-wide caldera ringed by three islands. Remnants of this volcano joined to create the pre-1883 Krakatau Island which collapsed during the major 1883 eruption. Anak Krakatau (Child of Krakatau), constructed beginning in late 1927 within the 1883 caldera (BGVN 44:03, figure 56), was the site of over 40 eruptive episodes until 22 December 2018 when a large explosion and flank collapse destroyed most of the 338-m-high edifice and generated a deadly tsunami (BGVN 44:03). The near-sea level crater lake inside the remnant of Anak Krakatau was the site of numerous small steam and tephra explosions from February (BGVN 44:08) through November 2019. A larger explosion in December 2019 produced the beginnings of a new cone above the surface of crater lake. Activity from August 2019 through January 2020 is covered in this report with information provided by the Indonesian Center for Volcanology and Geological Hazard Mitigation, referred to as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG). Aviation reports are provided by the Darwin Volcanic Ash Advisory Center (VAAC), and photographs are from the PVMBG webcam and visitors to the island.

Explosions were reported on more than ten days each month from August to October 2019. They were recorded based on seismicity, but webcam images also showed black tephra and steam being ejected from the crater lake to heights up to 450 m. Activity decreased significantly after the middle of November, although smaller explosions were witnessed by visitors to the island. After a period of relative quiet, a larger series of explosions at the end of December produced ash plumes that rose up to 3 km above the crater; the crater lake was largely filled with tephra after these explosions. Thermal activity persisted throughout the period of August 2019-January 2020. The wattage of Radiative Power increased from August through mid-October, and then decreased through January 2020 (figure 96).

Figure (see Caption) Figure 96. Thermal activity persisted at Anak Krakatau from 20 March 2019-January 2020. The wattage of Radiative Power increased from August through mid-October, and then decreased through January 2020. Courtesy of MIROVA.

Activity during August-November 2019. The new profile of Anak Krakatau rose to about 155 m elevation as of August 2019, almost 100 m less than prior to the December 2018 explosions and flank collapse (figure 97). Smaller explosions continued during August 2019 and were reported by PVMBG in 12 different VONAs (Volcano Observatory Notice to Aviation) on days 1, 3, 6, 17, 19, 22, 23, 25, and 28. Most of the explosions lasted for less than two minutes, according to the seismic data. PVMBG reported steam plumes of 25-50 m height above the sea-level crater on 20 and 21 August. They reported a visible ash cloud on 22 August; it rose to an altitude of 457 m and drifted NNE according to the VONA. In their daily update, they noted that the eruption plume of 250-400 m on 22 August was white, gray, and black. The Darwin VAAC reported that the ash plume was discernable on HIMAWARI-8 satellite imagery for a short period of time. PVMBG noted ten eruptions on 24 August with white, gray, and black ejecta rising 100-300 m. A webcam installed at month’s end provided evidence of diffuse steam plumes rising 25-150 m above the crater during 28-31 August.

Figure (see Caption) Figure 97. Only one tree survived on the once tree-covered spit off the NE end of Sertung Island after the December 2018 tsunami from Anak Krakatau covered it with ash and debris. The elevation of Anak Krakatau (center) was about 155 m on 8 August 2019, almost 100 m less than before the explosions and flank collapse. Panjang Island is on the left, and 746-m-high Rakata, the remnant of the 1883 volcanic island, is behind Anak Krakatau on the right. Courtesy of Amber Madden-Nadeau.

VONAs were issued for explosions on 1-3, 11, 13, 17, 18, 21, 24-27 and 29 September 2019. The explosion on 2 September produced a steam plume that rose 350 m, and dense black ash and ejecta which rose 200 m from the crater and drifted N. Gray and white tephra and steam rose 450 m on 13 and 17 September; ejecta was black and gray and rose 200 m on 21 September (figure 98). During 24-27 and 29 September tephra rose at least 200 m each day; some days it was mostly white with gray, other days it was primarily gray and black. All of the ejecta plumes drifted N. On days without explosions, the webcam recorded steam plumes rising 50-150 m above the crater.

Figure (see Caption) Figure 98. Explosions of steam and dark ejecta were captured by the webcam on Anak Krakatau on 21 (left) and 26 (right) September 2019. Courtesy of MAGMA Indonesia and PVMBG.

Explosions were reported daily during 12-14, 16-20, 25-27, and 29 October (figure 99). PVMBG reported eight explosions on 19 October and seven explosions the next day. Most explosions produced gray and black tephra that rose 200 m from the crater and drifted N. On many of the days an ash plume also rose 350 m from the crater and drifted N. The seismic events that accompanied the explosions varied in duration from 45 to 1,232 seconds (about 20 minutes). The Darwin VAAC reported the 12 October eruption as visible briefly in satellite imagery before dissipating near the volcano. The first of four explosions on 26 October also appeared in visible satellite imagery moving NNW for a short time. The webcam recorded diffuse steam plumes rising 25-150 m above the crater on most days during the month.

Figure (see Caption) Figure 99. A number of explosions at Anak Krakatau were captured by the webcam and visitors near the island during October 2019, shown here on the 12th, 14th, 17th, and 29th. Black and gray ejecta and steam plumes jetted several hundred meters high from the crater lake during the explosions. Webcam images courtesy of PVMBG and MAGMA Indonesia, with 12 October 2019 (top left) via VolcanoYT. Bottom left photo on 17 October courtesy of Christoph Sator.

Five VONAs were issued for explosions during 5-7 November, and one on 13 November 2019. The three explosions on 5 November produced 200-m-high plumes of steam and gray and black ejecta and ash plumes that rose 200, 450, and 550 m respectively; they all drifted N (figure 100). The Darwin VAAC reported ash drifting N in visible imagery for a brief period also. A 350-m-high ash plume accompanied 200-m-high ejecta on 6 November. Tephra rose 150-300 m from the crater during a 43 second explosion on 7 November. The explosion reported by PVMBG on 13 November produced black tephra and white steam 200 m high that drifted N. For the remainder of the month, when not obscured by fog, steam plumes rose daily 25-150 m from the crater.

Figure (see Caption) Figure 100. PVMBG’s KAWAH webcam captured an explosion with steam and dark ejecta from the crater lake at Anak Krakatau on 5 November 2019. Courtesy of PVMBG and MAGMA Indonesia.

A joint expedition with PVMBG and the Earth Observatory of Singapore (EOS) installed geophysical equipment on Anak Krakatau and Rakata during 12 and 13 November 2019 (figure 101). Visitors to the island during 19-23 and 22-24 November recorded the short-lived landscape and continuing small explosions of steam and black tephra from the crater lake (figures 102 and 103).

Figure (see Caption) Figure 101. A joint expedition to Anak Krakatau with PVMBG and the Earth Observatory of Singapore (EOS) installed geophysical equipment on Anak Krakatau and Rakata (background, left) during 12 and 13 November 2019. Images of the crater lake from the same spot (left) in December and January show the changes at the island (figure 108). Monitoring equipment installed near the shore sits over the many layers of ash and tephra that make up the island (right). Courtesy of Anna Perttu.
Figure (see Caption) Figure 102.The crater lake at Anak Krakatau during a 19-23 November 2019 visit was the site of continued explosions with jets of steam and tephra that rose as high as 30 m. Courtesy of Andrey Nikiforov and Volcano Discovery, used with permission.
Figure (see Caption) Figure 103. The landscape of Anak Krakatau recorded the rapidly evolving sequence of volcanic events during November 2019. Fresh ash covered recent lava near the shoreline on 22 November 2019 (top left). Large blocks of gray tephra (composed of other tephra fragments) were surrounded by reddish brown smaller fragments in the area between the crater and the ocean on 23 November 2019 (top right). Explosions of steam and black tephra rose tens of meters from the crater lake on 23 November 2019 (bottom). Courtesy of and copyright by Pascal Blondé.

Activity during December 2019-January 2020. Very little activity was recorded for most of December 2019. The webcam captured daily images of diffuse steam plumes rising 25-50 m above the crater which occasionally rose to 150 m. A new explosion on 28 December produced black and gray ejecta 200 m high that drifted N; the explosion was similar to those reported during August-November. A new series of explosions from 30 December 2019 to 1 January 2020 produced ash plumes which rose significantly higher than the previous explosions, reaching 2.4-3.0 km altitude and drifting S, E, and SE according to PVMBG (figure 104). They were initially visible in satellite imagery and reported drifting SW by the Darwin VAAC. By 31 December meteorological clouds prevented observation of the ash plume but a hotspot remained visible for part of that day.

Figure (see Caption) Figure 104.The KAWAH webcam at Anak Krakatau captured this image of incandescent ejecta exploding from the crater lake on 30 December 2019 near the start of a new sequence of large explosions. Courtesy of PVMBG and Alex Bogár.

The explosions on 30 and 31 December 2019 were captured in satellite imagery (figure 105) and appeared to indicate that the crater lake was largely destroyed and filled with tephra from a new growing cone, according to Simon Carn. This was confirmed in both satellite imagery and ground-based photography in early January (figures 106 and 107).

Figure (see Caption) Figure 105. Satellite imagery of the explosions at Anak Krakatau on 30 and 31 December 2019 showed dense steam rising from the crater (left) and a thermal anomaly visible through moderate cloud cover (right). Left image courtesy of Simon Carn, and copyright by Planet Labs, Inc. Right image uses Atmospheric Penetration rendering (bands 12, 11, and 8a) to show the thermal anomaly at the base of the steam plume, courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 106. Sentinel-2 images of Anak Krakatau before (left, 21 December 2019) and after (right, 13 January 2020) explosions on 30 and 31 December 2019 show the filling in of the crater lake with new volcanic material. Natural color rendering based on bands 4,3, and 2. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 107. The crater lake at Anak Krakatau changed significantly between the first week of December 2019 (left) and 8 January 2020 (right) after explosions on 30 and 31 December 2019. Compare with figure 101, taken from the same location in mid-November 2019. Left image courtesy of Piotr Smieszek. Right image courtesy of Peter Rendezvous.

Steam plumes rose 50-200 m above the crater during the first week of January 2020. An explosion on 7 January produced dense gray ash that rose 200 m from the crater and drifted E. Steam plume heights varied during the second week, with some plumes reaching 300 m above the crater. Multiple explosions on 15 January produced dense, gray and black ejecta that rose 150 m. Fog obscured the crater for most of the second half of the month; for a brief period, diffuse steam plumes were observed 25-1,000 m above the crater.

General Reference: Perttu A, Caudron C, Assink J D, Metz D, Tailpied D, Perttu B, Hibert C, Nurfiani D, Pilger C, Muzli M, Fee D, Andersen O L, Taisne B, 2020, Reconstruction of the 2018 tsunamigenic flank collapse and eruptive activity at Anak Krakatau based on eyewitness reports, seismo-acoustic and satellite observations, Earth and Planetary Science Letters, 541:116268. https://doi.org/10.1016/j.epsl.2020.116268.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/); Amber Madden-Nadeau, Oxford University (URL: https://www.earth.ox.ac.uk/people/amber-madden-nadeau/, https://twitter.com/AMaddenNadeau/status/1159458288406151169); Anna Perttu, Earth Observatory of Singapore (URL: https://earthobservatory.sg/people/anna-perttu); Simon Carn, Michigan Tech University (URL: https://www.mtu.edu/geo/department/faculty/carn/; https://twitter.com/simoncarn/status/1211793124089044994); VolcanoYT, Indonesia (URL: https://volcanoyt.com/, https://twitter.com/VolcanoYTz/status/1182882409445904386/photo/1; Christoph Sator (URL: https://twitter.com/ChristophSator/status/1184713192670281728/photo/1); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Pascal Blondé, France (URL: https://pascal-blonde.info/portefolio-krakatau/, https://twitter.com/rajo_ameh/status/1199219837265960960); Alex Bogár, Budapest (URL: https://twitter.com/AlexEtna/status/1211396913699991557); Piotr (Piter) Smieszek, Yogyakarta, Java, Indonesia (URL: http://www.lombok.pl/, https://twitter.com/piotr_smieszek/status/1204545970962231296); Peter Rendezvous (URL: https://www.facebook.com/peter.rendezvous ); Wulkany swiata, Poland (URL: http://wulkanyswiata.blogspot.com/, https://twitter.com/Wulkany1/status/1214841708862693376).


Mayotte (France) — March 2020 Citation iconCite this Report

Mayotte

France

12.83°S, 45.17°E; summit elev. 660 m

All times are local (unless otherwise noted)


Seismicity and deformation, with submarine E-flank volcanism starting in July 2018

Mayotte is a volcanic island in the Comoros archipelago between the eastern coast of Africa and the northern tip of Madagascar. A chain of basaltic volcanism began 10-20 million years ago and migrating W, making up four principal volcanic islands, according to the Institut de Physique du Globe de Paris (IPGP) and Cesca et al. (2020). Before May 2010, only two seismic events had been felt by the nearby community within recent decades. New activity since May 2018 consists of dominantly seismic events and lava effusion. The primary source of information for this report through February 2020 comes from semi-monthly reports from the Réseau de Surveillance Volcanologique et Sismologique de Mayotte (REVOSIMA), a cooperative program between the Institut de Physique du Globe de Paris (IPGP), the Bureau de Recherches Géologiques et Minières (BRGM), and the Observatoire Volcanologique du Piton de la Fournaise (OVPF-IPGP); Lemoine et al. (2019), the Centre National de la Recherche Scientifique (CNRS), and the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER).

Seismicity was the dominant type of activity recorded in association with a new submarine eruption. On 10 May 2018, the first seismic event occurred at 0814, detected by the YTMZ accelerometer from the French RAP Network, according to BRGM and Lemoine et al. (2019). Seismicity continued to increase during 13-15 May 2018, with the strongest recorded event for the Comoros area occurring on 15 May at 1848 and two more events on 20-21 May (figure 1). At the time, no surface effusion were directly observed; however, Global Navigation Satellite System (GNSS) instruments were deployed to monitor any ground motion (Lemoine et al. 2019).

Figure (see Caption) Figure 1. A graph showing the number of daily seismic events greater than M 3.5 occurring offshore of Mayotte from 10 May 2018 through 15 February 2020. Seismicity significantly decreased in July 2018, but continued intermittently through February 2020, with relatively higher seismicity recorded in late August and mid-September 2018. Courtesy of IPGP and REVOSIMA.

Seismicity decreased dramatically after June 2018, with two spikes in August and September (see figure 1). Much of this seismicity occurred offshore 50 km E of Mayotte Island (figure 2). The École Normale Supérieure, the Observatoire Volcanologique du Piton de la Fournaise (OVPF-IPGP), and the REVOSIMA August 2019 bulletin reported that measurements from the GNSS stations and Teria GPS network data indicated eastward surface deformation and subsidence beginning in July 2018. Based on this ground deformation data Lemoine et al. (2019) determined that the eruptive phase began fifty days after the initial seismic events occurred, on 3 July 2018.

Figure (see Caption) Figure 2. Maps of seismic activity offshore near Mayotte during May 2019. Seismic swarms occurred E of Mayotte Island (top) and continued in multiple phases through October 2019. New lava effusions were observed 50 km E of Petite Terre (bottom). Bottom image has been modified with annotations; courtesy of IPGP, BRGM, IFREMER, CNRS, and University of Paris.

Between 2 and 18 May 2019, an oceanographic campaign (MAYOBS 1) discovered a new submarine eruption site 50 km E from the island of Mayotte (figure 2). The director of IPGP, Marc Chaussidon, stated in an interview with Science Magazine that multibeam sonar waves were used to determine the elevation (800 m) and diameter (5 km) of the new submarine cone (figure 3). In addition, this multibeam sonar image showed fluid plumes within the water column rising from the center and flanks of the structure. According to REVOSIMA, these plumes rose to 1 km above the summit of the cone but did not breach the ocean surface. The seafloor image (figure 3) also indicated that as much as 5 km3 of magma erupted onto the seafloor from this new edifice during May 2019, according to Science Magazine.

Figure (see Caption) Figure 3. Seafloor image of the submarine vent offshore of Mayotte created with multibeam sonar from 2 to 18 May 2019. The red line is the outline of the volcanic cone located at approximately 3.5 km depth. The blue-green color rising from the peak of the red outline represents fluid plumes within the water column. Courtesy of IPGP.

On 17 May 2019, a second oceanographic campaign (MAYOBS 2) discovered new lava flows located 5 km S of the new eruptive site. BRGM reported that in June a new lava flow had been identified on the W flank of the cone measuring 150 m thick with an estimated volume of 0.3 km3 (figure 4). According to REVOSIMA, the presence of multiple new lava flows would suggest multiple effusion points. Over a period of 11 months (July 2018-June 2019) the rate of lava effusion was at least 150-200 m3/s; between 18 May to 17 June 2019, 0.2 km3 of lava was produced, and from 17 June to 30 July 2019, 0.3 km3 of lava was produced. The MAYOBS 4 (19 July 2019-4 August 2019) and SHOM (20-21 August 2019) missions revealed a new lava flow formed between 31 July and 20 August to the NW of the eruptive site with a volume of 0.08 km3 and covering 3.25 km2.

Figure (see Caption) Figure 4. Bathymetric map showing the location of the new lava flow on the W flank of the submarine cone offshore to the E of Mayotte Island. The MAYOBS 2 campaign was launched in June 2019 (left) and MAYOBS 4 was launched in late July 2019 (right). Courtesy of BRGM.

During the MAYOBS 4 campaign in late July 2019, scientists dredged the NE flank of the cone for samples and took photographs of the newly erupted lava (figure 5). Two dives found the presence of pillow lavas. When samples were brought up to the surface, they exploded due to the large amount of gas and rapid decompression.

Figure (see Caption) Figure 5. Photographs taken using the submersible interactive camera system (SCAMPI) of newly formed pillow lavas (top) and a vesicular sample (bottom) dredged near the new submarine eruptive site at Mayotte in late July 2019. Courtesy of BRGM.

During April-May 2019 the rate of ground deformation slowed. Deflation was also observed up to 90 km E of Mayotte in late October 2019 and consistently between August 2019 and February 2020. Seismicity continued intermittently through February 2020 offshore E of Mayotte Island, though the number of detected events started to decrease in July 2018 (see figure 1). Though seismicity and deformation continued, the most recent observation of new lava flows occurred during the MAYOBS 4 and SHOM campaigns on 20 August 2019, as reported in REVOSIMA bulletins.

References: Cesca S, Heimann S, Letort J, Razafindrakoto H N T, Dahm T, Cotton F, 2020. Seismic catalogues of the 2018-2019 volcano-seismic crisis offshore Mayotte, Comoro Islands. Nat. Geosci. 13, 87-93. https://doi.org/10.1038/s41561-019-0505-5.

Lemoine A, Bertil D, Roulle A, Briole P, 2019. The volcano-tectonic crisis of 2018 east of Mayotte, Comoros islands. Preprint submitted to EarthArXiv, 28 February 2019. https://doi.org/10.31223/osf.io/d46xj.

Geologic Background. Mayotte, located in the Mozambique Channel between the northern tip of Madagascar and the eastern coast of Africa, consists two main volcanic islands, Grande Terre and Petite Terre, and roughly twenty islets within a barrier-reef lagoon complex (Zinke et al., 2005; Pelleter et al., 2014). Volcanism began roughly 15-10 million years ago (Pelleter et al., 2014; Nougier et al., 1986), and has included basaltic lava flows, nephelinite, tephrite, phonolitic domes, and pyroclastic deposits (Nehlig et al., 2013). Lavas on the NE were active from about 4.7 to 1.4 million years and on the south from about 7.7 to 2.7 million years. Mafic activity resumed on the north from about 2.9 to 1.2 million years and on the south from about 2 to 1.5 million years. Several pumice layers found in cores on the barrier reef-lagoon complex indicate that volcanism likely occurred less than 7,000 years ago (Zinke et al., 2003). More recent activity that began in May 2018 consisted of seismicity and ground deformation occurring offshore E of Mayotte Island (Lemoine et al., 2019). One year later, in May 2019, a new subaqueous edifice and associated lava flows were observed 50 km E of Petite Terre during an oceanographic campaign.

Information Contacts: Réseau de Surveillance Volcanologique et Sismologique de Mayotte (REVOSIMA), a cooperative program of a) Institut de Physique du Globe de Paris (IPGP), b) Bureau de Recherches Géologiques et Minières (BRGM), c) Observatoire Volcanologique du Piton de la Fournaise (OVPF-IPGP); (URL: http://www.ipgp.fr/fr/reseau-de-surveillance-volcanologique-sismologique-de-mayotte); Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); Bureau de Recherches Géologiques et Minières (BRGM), 3 avenue Claude-Guillemin, BP 36009, 45060 Orléans Cedex 2, France (URL: https://www.brgm.fr/); Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 1625 route de Sainte-Anne, CS 10070, 29280 Plouzané, France (URL: https://wwz.ifremer.fr/); Centre National de la Recherche Scientifique (CNRS), 3 rue Michel-Ange, 75016 Paris, France (URL: http://www.cnrs.fr/); École Normale Supérieure, 45 rue d'Ulm, F-75230 Paris Cedex 05, France (URL: https://www.ens.psl.eu/); Université de Paris, 85 boulevard Saint-Germain, 75006 Paris, France (URL: https://u-paris.fr/en/498-2/); Roland Pease, Science Magazine (URL: https://science.sciencemag.org/, article at https://www.sciencemag.org/news/2019/05/ship-spies-largest-underwater-eruption-ever) published 21 May 2019.


Fernandina (Ecuador) — March 2020 Citation iconCite this Report

Fernandina

Ecuador

0.37°S, 91.55°W; summit elev. 1476 m

All times are local (unless otherwise noted)


Fissure eruption produced lava flows during 12-13 January 2020

Fernandina is a volcanic island in the Galapagos islands, around 1,000 km W from the coast of mainland Ecuador. It has produced nearly 30 recorded eruptions since 1800, with the most recent events having occurred along radial or circumferential fissures around the summit crater. The most recent previous eruption, starting on 16 June 2018, lasted two days and produced lava flows from a radial fissure on the northern flank. Monitoring and scientific reports come from the Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN).

A report from IG-EPN on 12 January 2020 stated that there had been an increase in seismicity and deformation occurring during the previous weeks. On the day of the report, 11 seismic events had occurred, with the largest magnitude of 4.7 at a depth of 5 km. Shortly before 1810 that day a circumferential fissure formed below the eastern rim of the La Cumbre crater, at about 1.3-1.4 km elevation, and produced lava flows down the flank (figure 39). A rapid-onset seismic swarm reached maximum intensity at 1650 on 12 January (figure 40); a second increase in seismicity indicating the start of the eruption began around 70 minutes later (1800). A hotspot was observed in NOAA / CIMSS data between 1800 and 1810, and a gas plume rising up to 2 km above the fissure dispersed W to NW. The eruption lasted 9 hours, until about 0300 on 13 January.

Figure (see Caption) Figure 39. Lava flows erupting from a circumferential fissure on the eastern flank of Fernandina on 12 January 2020. Photos courtesy of Parque Nacional Galápagos.
Figure (see Caption) Figure 40. Graph showing the Root-Mean-Square (RMS) amplitude of the seismic signals from the FER-1 station at Fernandina on 12-13 January 2020. The graph shows the increase in seismicity leading to the eruption on the 12th (left star), a decrease in the seismicity, and then another increase during the event (right star). Courtesy of S. Hernandez, IG-EPN (Report on 13 January 2020).

A report issued at 1159 local time on 13 January 2020 described a rapid decrease in seismicity, gas emissions, and thermal anomalies, indicating a rapid decline in eruptive activity similar to previous events in 2017 and 2018. An overflight that day confirmed that the eruption had ended, after lava flows had extended around 500 m from the crater and covered an area of 3.8 km2 (figures 41 and 42). Seismicity continued on the 14th, with small volcano-tectonic (VT) earthquakes occurring less than 500 m below the surface. Periodic seismicity was recorded through 13-15 January, though there was an increase in seismicity during 17-22 January with deformation also detected (figure 43). No volcanic activity followed, and no additional gas or thermal anomalies were detected.

Figure (see Caption) Figure 41. The lava flow extents at Fernandina of the previous two eruptions (4-7 September 2017 and 16-21 June 2018) and the 12-13 January 2020 eruption as detected by FIRMS thermal anomalies. Thermal data courtesy of NASA; figure prepared by F. Vásconez, IG-EPN (Report on 13 January 2020).
Figure (see Caption) Figure 42. This fissure vent that formed on the E flank of Fernandina on 12 January 2020 produced several lava flows. A weak gas plume was still rising when this photo was taken the next day, but the eruption had ceased. Courtesy of Parque Nacional Galápagos.
Figure (see Caption) Figure 43. Soil displacement map for Fernandina during 10 and 16 January 2020, with the deformation generated by the 12 January eruption shown. Courtesy of IG-EPN (Report on 23 January 2020).

Geologic Background. Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Dirección del Parque Nacional Galápagos (DPNG), Isla Santa Cruz, Galápagos, Ecuador (URL: http://www.galapagos.gob.ec/).


Masaya (Nicaragua) — February 2020 Citation iconCite this Report

Masaya

Nicaragua

11.985°N, 86.165°W; summit elev. 594 m

All times are local (unless otherwise noted)


Lava lake persists with lower temperatures during August 2019-January 2020

Masaya is a basaltic caldera located in Nicaragua and contains the Nindirí, San Pedro, San Juan, and Santiago craters. The currently active Santiago crater hosts a lava lake, which has remained active since December 2015 (BGVN 41:08). The primary source of information for this August 2019-January 2020 report comes from the Instituto Nicareguense de Estudios Territoriales (INETER) and satellite -based imagery and thermal data.

On 16 August, 13 September, and 11 November 2019, INETER took SO2 measurements by making a transect using a mobile DOAS spectrometer that sampled for gases downwind of the volcano. Average values during these months were 2,095 tons/day, 1,416 tons/day, and 1,037 tons/day, respectively. August had the highest SO2 measurements while those during September and November were more typical values.

Satellite imagery showed a constant thermal anomaly in the Santiago crater at the lava lake during August 2019 through January 2020 (figure 82). According to a news report, ash was expelled from Masaya on 15 October 2019, resulting in minor ashfall in Colonia 4 de Mayo (6 km NW). On 21 November thermal measurements were taken at the fumaroles and near the lava lake using a FLIR SC620 thermal camera (figure 83). The temperature measured 287°C, which was 53° cooler than the last time thermal temperatures were taken in May 2019.

Figure (see Caption) Figure 82. Sentinel-2 thermal satellite imagery showed the consistent presence of an active lava lake within the Santiago crater at Masaya during August 2019 through January 2020. Images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 83. Thermal measurements taken at Masaya on 21 November 2019 with a FLIR SC620 thermal camera that recorded a temperature of 287°C. Courtesy of INETER (Boletin Sismos y Volcanes de Nicaragua, Noviembre, 2019).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent low-power thermal anomalies compared to the higher-power ones before May 2019 (figure 84). The thermal anomalies were detected during August 2019 through January 2020 after a brief hiatus from early may to mid-June.

Figure (see Caption) Figure 84. Thermal anomalies occurred intermittently at Masaya during 21 February 2019 through January 2020. Courtesy of MIROVA.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The Nindirí and Masaya cones, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals have caused health hazards and crop damage.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); La Jornada (URL: https://www.lajornadanet.com/, article at https://www.lajornadanet.com/index.php/2019/10/16/volcan-masaya-expulsa-cenizas/#.Xl6f8ahKjct).


Reventador (Ecuador) — February 2020 Citation iconCite this Report

Reventador

Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

All times are local (unless otherwise noted)


Nearly daily ash emissions and frequent incandescent block avalanches August 2019-January 2020

Reventador is an andesitic stratovolcano located in the Cordillera Real, Ecuador. Historical eruptions date back to the 16th century, consisting of lava flows and explosive events. The current eruptive activity has been ongoing since 2008 with previous activity including daily explosions with ash emissions, and incandescent block avalanches (BGVN 44:08). This report covers volcanism from August 2019 through January 2020 using information primarily from the Instituto Geofísico (IG-EPN), the Washington Volcano Ash Advisory Center (VAAC), and various infrared satellite data.

During August 2019 to January 2020, IG-EPN reported almost daily explosive eruptions and ash plumes. September had the highest average of explosive eruptions while January 2020 had the lowest (table 11). Ash plumes rose between a maximum of 1.2 to 2.5 km above the crater during this reporting period with the highest plume height recorded in December. The largest amount of SO2 gases produced was during the month of October with 502 tons/day. Frequently at night during this reporting period, crater incandescence was observed and was occasionally accompanied by incandescent block avalanches traveling as far as 900 m downslope from the summit of the volcano.

Table 11. Monthly summary of eruptive events recorded at Reventador from August 2019 through January 2020. Data courtesy of IG-EPN (August to January 2020 daily reports).

Month Average Number of Explosions Max plume height above the crater Max SO2
Aug 2019 26 1.6 km --
Sep 2019 32 1.7 km 428 tons/day
Oct 2019 29 1.3 km 502 tons/day
Nov 2019 25 1.2 km 432 tons/day
Dec 2019 25 2.5 km 331 tons/day
Jan 2020 12 1.7 km --

During the month of August 2019, between 11 and 45 explosions were recorded every day, frequently accompanied by gas-and-steam and ash emissions (figure 119); plumes rose more than 1 km above the crater on nine days. On 20 August the ash plume rose to a maximum 1.6 km above the crater. Summit incandescence was seen at night beginning on 10 August, continuing frequently throughout the rest of the reporting period. Incandescent block avalanches were reported intermittently beginning that same night through 26 January 2020, ejecting material between 300 to 900 m below the summit and moving on all sides of the volcano.

Figure (see Caption) Figure 119. An ash plume rising from the summit of Reventador on 1 August 2019. Courtesy of Radio La Voz del Santuario.

Throughout most of September 2019 gas-and-steam and ash emissions were observed almost daily, with plumes rising more than 1 km above the crater on 15 days, according to IG-EPN. On 30 September, the ash plume rose to a high of 1.7 km above the crater. Each day, between 18 and 72 explosions were reported, with the latter occurring on 19 September. At night, crater incandescence was commonly observed, sometimes accompanied by incandescent material rolling down every flank.

Elevated seismicity was reported during 8-15 October 2019 and almost daily gas-and-steam and ash emissions were present, ranging up to 1.3 km above the summit. Every day during this month, between 13 and 54 explosions were documented and crater incandescence was commonly observed at night. During November 2019, gas-and-steam and ash emissions rose greater than 1 km above the crater except for 10 days; no emissions were reported on 29 November. Daily explosions ranged up to 42, occasionally accompanied by crater incandescence and incandescent ejecta.

Washington VAAC notices were issued almost daily during December 2019, reporting ash plumes between 4.6 and 6 km altitude throughout the month and drifting in multiple directions. Each day produced 5-52 explosions, many of which were accompanied by incandescent blocks rolling down all sides of the volcano up to 900 m below the summit. IG-EPN reported on 11 December that a gas-and-steam and ash emission column rose to a maximum height of 2.5 km above the crater, drifting SW as was observed by satellite images and reported by the Washington VAAC.

Volcanism in January 2020 was relatively low compared to the other months of this reporting period. Explosions continued on a nearly daily basis early in the month, ranging from 20 to 51. During 5-7 January incandescent material ejected from the summit vent moved as block avalanches downslope and multiple gas-and-steam and ash plumes were produced (figures 120, 121, and 122). After 9 January the number of explosions decreased to 0-16 per day. Ash plumes rose between 4.6 and 5.8 km altitude, according to the Washington VAAC.

Figure (see Caption) Figure 120. Night footage of activity on 5 (top) and 6 (bottom) January 2020 at the summit of Reventador, producing a dense, dark gray ash plume and ejecting incandescent material down multiple sides of the volcano. This activity is not uncommon during this reporting period. Courtesy of Martin Rietze, used with permission.
Figure (see Caption) Figure 121. An explosion at Reventador on 7 January 2020, which produced a dense gray ash plume. Courtesy of Martin Rietze, used with permission.
Figure (see Caption) Figure 122. Night footage of the evolution of an eruption on 7 January 2020 at the summit of Reventador, which produced an ash plume and ejected incandescent material down multiple sides of the volcano. Courtesy of Martin Rietze, used with permission.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent and strong thermal anomalies within 5 km of the summit during 21 February 2019 through January 2020 (figure 123). In comparison, the MODVOLC algorithm reported 24 thermal alerts between August 2019 and January 2020 near the summit. Some thermal anomalies can be seen in Sentinel-2 thermal satellite imagery throughout this reporting period, even with the presence of meteorological clouds (figure 124). These thermal anomalies were accompanied by persistent gas-and-steam and ash plumes.

Figure (see Caption) Figure 123. Thermal anomalies at Reventador persisted during 21 February 2019 through January 2020 as recorded by the MIROVA system (Log Radiative Power). Courtesy of MIROVA.
Figure (see Caption) Figure 124. Sentinel-2 thermal satellite images of Reventador from August 2019 to January 2020 showing a thermal hotspot in the central summit crater summit. In the image on 7 January 2020, the thermal anomaly is accompanied by an ash plume. Courtesy of Sentinel Hub Playground.

Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Radio La Voz del Santuario (URL: https://www.facebook.com/Radio-La-Voz-del-Santuario-126394484061111/, posted at: https://www.facebook.com/permalink.php?story_fbid=2630739100293291&id=126394484061111); Martin Rietze, Taubenstr. 1, D-82223 Eichenau, Germany (URL: https://mrietze.com/, https://www.youtube.com/channel/UC5LzAA_nyNWEUfpcUFOCpJw/videos).


Pacaya (Guatemala) — February 2020 Citation iconCite this Report

Pacaya

Guatemala

14.382°N, 90.601°W; summit elev. 2569 m

All times are local (unless otherwise noted)


Continuous explosions, small cone, and lava flows during August 2019-January 2020

Pacaya is a highly active basaltic volcano located in Guatemala with volcanism consisting of frequent lava flows and Strombolian explosions originating in the Mackenney crater. The previous report summarizes volcanism that included multiple lava flows, Strombolian activity, avalanches, and gas-and-steam emissions (BGVN 44:08), all of which continue through this reporting period of August 2019 to January 2020. The primary source of information comes from reports by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) in Guatemala and various satellite data.

Strombolian explosions occurred consistently throughout this reporting period. During the month of August 2019, explosions ejected material up to 30 m above the Mackenney crater. These explosions deposited material that contributed to the formation of a small cone on the NW flank of the Mackenney crater. White and occasionally blue gas-and-steam plumes rose up to 600 m above the crater drifting S and W. Multiple incandescent lava flows were observed traveling down the N and NW flanks, measuring up to 400 m long. Small to moderate avalanches were generated at the front of the lava flows, including incandescent blocks that measured up to 1 m in diameter. Occasionally incandescence was observed at night from the Mackenney crater.

In September 2019 seismicity was elevated compared to the previous month, registering a maximum of 8,000 RSAM (Realtime Seismic Amplitude Measurement) units. White and occasionally blue gas-and-steam plumes that rose up to 1 km above the crater drifted generally S as far as 3 km from the crater. Strombolian explosions continued, ejecting material up to 100 m above the crater rim. At night and during the early morning, crater incandescence was observed. Incandescent lava flows traveled as much as 600 m down the N and NW flanks toward the Cerro Chino crater (figure 116). On 21 September two lava flows descended the SW flank. Constant avalanches with incandescent blocks measuring 1 m in diameter occurred from the front of many of these lava flows.

Figure (see Caption) Figure 116. Webcam image of Pacaya on 25 September 2019 showing thermal signatures and the point of emission on the NNW flank at night using Landsat 8 (Nocturnal) imagery (left) and a daytime image showing the location of these lava effusions (right) along with gas-and-steam emissions from the active crater. Courtesy of INSIVUMEH.

Weak explosions continued through October 2019, ejecting material up to 75 m above the crater and building a small cone within the crater. White and occasionally blue gas-and-steam plumes rose 400-800 m above the crater, drifting W and NW and extending up to 4 km from the crater during the week of 26 October-1 November. Lava flows measuring up to 250 m long, originating from the Mackenney crater were descending the N and NW flanks (figure 117). Avalanches carrying large blocks 1 m in diameter commonly occurred at the front of these lava flows.

Figure (see Caption) Figure 117. Photo of lava flows traveling down the flanks of Pacaya taken between 28 September 2019 and 4 October. Courtesy of INSIVUMEH (28 September 2019 to 4 October Weekly Report).

Continuing Strombolian explosions in November 2019 ejected material 15-75 m above the crater, which then contributed to the formation of the new cone. White and occasionally blue gas-and-steam plumes rose 100-600 m above the crater drifting in different directions and extending up to 2 km. Multiple lava flows from the Mackenney crater moving down all sides of the volcano continued, measuring 50-700 m long. Avalanches were generated at the front of the lava flows, often moving blocks as large as 1 m in diameter. The number of lava flows decreased during 2-8 November and the following week of 9-15 November no lava flows were observed, according to INSIVUMEH. During the week of 16-22 November, a small collapse occurred in the Mackenney crater and explosive activity increased during 16, 18, and 20 November, reaching RSAM units of 4,500. At night and early morning in late November crater incandescence was visible. On 24 November two lava flows descended the NW flank toward the Cerro Chino crater, measuring 100 m long.

During December 2019, much of the activity remained the same, with Strombolian explosions originating from two emission points in the Mackenney crater ejecting material 75-100 m above the crater; white and occasionally blue gas-and-steam plumes to 100-300 m above the crater drifted up to 1.5 km downwind to the S and SW. Lava flows descended the S and SW flanks reaching 250-600 m long (figure 118). On 29 December seismicity increased, reaching 5,000 RSAM units.

Figure (see Caption) Figure 118. Lava flows moving to the S and SW at Pacaya on 31 December 2019. Courtesy of INSIVUMEH (28 December 2019 to 3 January 2020 Weekly Report).

Consistent Strombolian activity continued into January 2020 ejecting material 25-100 m above the crater. These explosions deposited material inside the Mackenney crater, contributing to the formation of a small cone. White and occasionally blue fumaroles consisting of mostly water vapor were observed drifting in different directions. At night, summit incandescence and lava flows were visible descending the N, NW, and S flanks with the flow on the NW flank traveling toward the Cerro Chino crater.

During August 2019 through January 2020, multiple lava flows and bright thermal anomalies (yellow-orange) within the crater were seen in Sentinel-2 thermal satellite imagery (figures 119 and 120). In addition, constant strong thermal anomalies were detected by the MIROVA (Middle InfraRed Observation of Volcanic Activity) system during 21 February 2019 through January 2020 within 5 km of the summit (figure 121). A slight decrease in energy was seen from May to June and August to September. Energy increased again between November and December. According to the MODVOLC algorithm, 37 thermal alerts were recorded during August 2019 through January 2020.

Figure (see Caption) Figure 119. Sentinel-2 thermal satellite images of Pacaya showing thermal activity (bright yellow-orange) during August 2019 to November. All images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 120. Sentinel-2 thermal satellite images of Pacaya showing thermal activity (bright yellow-orange) during December 2019 through January 2020. All images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 121. The MIROVA thermal activity graph (log radiative power) at Pacaya during 21 February 2019 to January 2020 shows strong, frequent thermal anomalies through January with a slight decrease in energy between May 2019 to June 2019 and August 2019 to September 2019. Courtesy of MIROVA.

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Kikai (Japan) — February 2020 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Single explosion with steam and minor ash, 2 November 2019

The 19-km-wide submerged Kikai caldera at the N end of Japan’s Ryukyu Islands was the source of one of the world's largest Holocene eruptions about 6,300 years ago, producing large pyroclastic flows and abundant ashfall. During the last century, however, only intermittent minor ash emissions have characterized activity at Satsuma Iwo Jima island, the larger subaerial fragment of the Kikai caldera; several events have included limited ashfall in communities on nearby islands. The most recent event was a single day of explosions on 4 June 2013 that produced ash plumes and minor ashfall on the flank. A minor episode of increased seismicity and fumarolic activity was reported in late March 2018, but no ash emissions were reported. A new single-day event on 2 November 2019 is described here with information provided by the Japan Meteorological Agency (JMA).

JMA reduced the Alert Level to 1 on 27 April 2018 after a brief increase in seismicity during March 2018 (BGVN 45:05); no significant changes in volcanic activity were observed for the rest of the year. Steam plumes rose from the summit crater to heights around 1,000 m; the highest plume rose 1,800 m. Occasional nighttime incandescence was recorded by high-sensitivity surveillance cameras. SO2 measurements made during site visits in March, April, and May indicated amounts ranging from 300-1,500 tons per day, similar to values from 2017 (400-1,000 tons per day). Infrared imaging devices indicated thermal anomalies from fumarolic activity persisted on the N and W flanks during the three site visits. A field survey of the SW flank on 25 May 2018 confirmed that the crater edge had dropped several meters into the crater since a similar survey in April 2007. Scientists on a 19 December 2018 overflight had observed fumarolic activity.

There were no changes in activity through October 2019. Weak incandescence at night continued to be periodically recorded with the surveillance cameras (figure 9). A brief eruption on 2 November 2019 at 1735 local time produced a gray-white plume that rose slightly over 1,000 m above the Iodake crater rim (figure 10). As a result, JMA raised the Alert Level from 1 to 2. During an overflight the following day, a steam plume rose a few hundred meters above the summit, but no further activity was observed. No clear traces of volcanic ash or other ejecta were found around the summit (figure 11). Infrared imaging also showed no particular changes from previous measurements. Discolored seawater continued to be observed around the base of the island in several locations.

Figure (see Caption) Figure 9. Incandescence at night on 25 October 2019 was observed at Satsuma Iwo Jima (Kikai) with the Iwanogami webcam. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 1st year of Reiwa [2019]).
Figure (see Caption) Figure 10. The Iwanogami webcam captured a brief gray-white ash and steam emission rising above the Iodake crater rim on Satsuma Iwo Jima (Kikai) on 2 November 2019 at 1738 local time. The plume rose slightly over 1,000 m before dissipating. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 1st year of Reiwa [2019]).
Figure (see Caption) Figure 11. During an overflight of Satsuma Iwo Jima (Kikai) on 3 November 2019 no traces of ash were seen from the previous day’s explosion; only steam plumes rose a few hundred meters above the summit, and discolored water was present in a few places around the shoreline. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 1st year of Reiwa [2019]).

For the remainder of November 2019, steam plumes rose up to 1,300 m above the summit, and nighttime incandescence was occasionally observed in the webcam. Seismic activity remained low and there were no additional changes noted through January 2020.

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. It was the source of one of the world's largest Holocene eruptions about 6,300 years ago when rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km E of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html).


Nevado del Ruiz (Colombia) — January 2020 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


Intermittent ash, gas-and-steam, and SO2 plumes, and thermal anomalies during January 2018-December 2019

Nevado del Ruiz is a glaciated stratovolcano located in Colombia. It is most known for the eruption on 13 November 1985 that produced an ash plume and pyroclastic flows onto the glacier, triggering a lahar and killing approximately 25,000 people in the towns of Armero (46 km W) and Chinchiná (34 km E). Since the September 1985-July 1991 eruption, volcanism has occurred dominantly at the Arenas crater, with eruptive periods during February 2012-July 2013 and November 2014-May 2017 (BGVN 42:06 and 44:12). The previous eruption included ash and gas-and-steam plumes, ashfall, and thermal anomalies through May 2017, after which no clear observations of ongoing activity were available until an ash plume was seen in satellite and webcam images on 18 December 2017. This report provides data and observations from January 2018 through December 2019 using information primarily from reports by the Servicio Geologico Colombiano and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various satellite data.

Summary of activity during December 2017-December 2019. Although data is incomplete, the current eruptive period is considered to have begun with the emission of an ash plume on 18 December 2017. The Washington VAAC issued an advisory that day for an ash plume to 6 km that was moving west and dispersing, further describing it as a "thin veil of volcanic ash and gasses" that was seen in visible satellite imagery, NOAA/CIMSS, and supported by webcam imagery.

Reports of significant ash plumes visible in satellite imagery were infrequent in 2018 and 2019, with a few notable pulses in July 2018, February-March 2019, and August-September 2019 (figure 95). Sentinel-2 thermal satellite data in comparison with Suomi NPP/VIIRS sensor data, and the MODVOLC algorithm for MODIS data registered infrared thermal hotspots intermittently throughout 2018 to 2019 with more frequent anomalies during January-March 2018, August 2018, October 2018-February 2019, and November-December 2019; observations during March-June of each year were low. Identification of SO2 emissions were frequent and consistent during all of 2018-2019 (figure 96).

Figure (see Caption) Figure 95. Timeline summary of observed activity at Nevado del Ruiz from January 2018 through December 2019. VAAC reports typically indicate a significant ash plume. Satellite-based SO2 data is variable with respect to volume of emitted gas, but reflects a point source at the volcano. For Sentinel-2, MODVOLC, and VIIRS data, the dates indicated represents detected thermal anomalies. White areas indicate no activity was observed, which may also be due to meteoric clouds. Data courtesy of Washington VAAC, NASA Goddard Space Flight Center, Sentinel Hub Playground, HIGP, and NASA Worldview using the "Fire and Thermal Anomalies" layer.
Figure (see Caption) Figure 96. Examples of SO2 plumes from Nevado del Ruiz detected by the Aura/OMI instrument during 12 May (top left), 7 October (top middle), and 29 November 2018 (top right) and 9 January (bottom left), 30 March (bottom middle), and 6 October 2019 (bottom right). Courtesy of NASA Goddard Space Flight Center.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows weak thermal anomalies within 5 km of the summit occurring dominantly between October 2018 through March 2019 (figure 97). Between April and October 2019, the number of thermal anomalies was low, registering eight during this time. The number of thermal signatures increased at the beginning of November 2019 and continued through the rest of 2019.

Figure (see Caption) Figure 97. Weak thermal anomalies at Nevado del Ruiz for 25 September 2018 through December 2019 as recorded by the MIROVA system (log radiative power) occurred mostly during December 2018 through March 2019. Activity was low during April to October 2019 with renewed signatures in November 2019. Courtesy of MIROVA.

Seismicity that occurred during 2018-2019 was located mainly in the Arenas crater and consisted of low-frequency (LF) and very low-frequency (VLF) earthquakes and volcanic tremors, many of which were associated with minor gas-and-steam and ash emissions confirmed through webcams. The number of earthquakes reported by SGC fluctuated each week, but the energy remained relatively consistent. The highest magnitude earthquake that occurred during 2018 was on 26 October reaching 3.1 ML (local magnitude) and during 2019 the largest was 2.8 ML on 21 April.

Activity during 2018. Throughout 2018, gas-and-steam plumes, mostly composed of water vapor and sulfur dioxide frequently occurred, rising to a maximum of 2.2 km above the Arenas crater on 24 March. Weak thermal anomalies were seen intermittently in thermal satellite imagery from Sentinel-2 and NASA Worldview during 4 January through March and September to December (figure 98). Activity during March to April 2018 was relatively low and consisted dominantly of gas-and-steam emissions, low-energy seismicity, and intermittent thermal anomalies. Between 9 May and 5 August, no thermal signatures were detected.

Figure (see Caption) Figure 98. Sentinel-2 thermal satellite imagery detected thermal anomalies (bright yellow-orange) within the Arenas crater at Nevado del Ruiz that were mostly visible during the beginning and last months of 2018. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

Ash plumes were seen in GOES-EAST satellite imagery, through webcams, and by SGC personnel. The first ash plume of 2018 occurred on 21 April at 0800, six days after NASA Worldview detected a thermal anomaly within the Arenas crater. The plume rose 6 km altitude and drifted NW as seen in GOES-EAST satellite imagery and reported by the Washington VAAC. Weak gas-and-steam and ash emissions were confirmed by webcams on 22 July, associated with a volcanic tremor. On 11 August 2018, another ash plume was reported in a VAAC notice rising 6.7 km altitude drifting W. During the week of 21 August, SGC reported that seismicity in the Arenas crater was associated with minor gas-and-steam and ash emissions, as confirmed by webcams.

The number of ash plumes increased during September (figure 99), one of which reached a maximum altitude of 7.3 km on 2 September. On 5 September, a continuous volcanic tremor occurred and was accompanied by an ash plume rising 7 km altitude drifting W, according to a Washington VAAC report. Ashfall was observed during the week of 11 September in Manizales (30 km NW) and Villamaría (27 km NW). A new volcanic tremor occurred on 15 September and was accompanied by various ash emissions reaching 1.4 km above the crater and drifting NW as confirmed by PNNN, inhabitants within the vicinity of the volcano, and the Washington VAAC. Seismicity continuing into the weeks of 25 September and 2 October was also accompanied by ash emissions, rising to an altitude of 1.4 km above the crater on 22 September. The number of reported gas-and-steam and ash emissions decreased after September; ash emissions were reported by SGC on 19, 22, 26, and 31 October, 6, 9, and 17 November, and 14 December.

Figure (see Caption) Figure 99. Webcam images of gas-and-steam and ash plumes rising from Nevado del Ruiz during 2018. Courtesy of Servicio Geologico Colombiano.

Activity during 2019. Gas-and-steam and ash emissions continued intermittently through 2019, with an increased number of ash emissions compared to the previous year. Infrared hotspots were detected in Sentinel-2 satellite imagery primarily during January-February 2019 and December 2019, often accompanied by gas-and-steam emissions (figure 100). An ash plume was seen in GOES-EAST satellite imagery on 2 January 2019, rising to an altitude of 5.8 km and drifting NW, according to a Washington VAAC report. On 7 January, ashfall in Manizales and Villamaría was observed. A thermal hotspot was detected in multispectral imagery, according to a Washington VAAC report on 29 January. Slight ground deformation was observed by GNSS and electronic inclinometers during the weeks of 29 January and 10 September. Volcanism was relatively low during February to March and consisted of mostly gas-and-steam emissions and rare ash plumes; these ash emissions were reported on 2 and 9 February and 16 March by the Washington VAAC rising between 5.8-6.7 km altitude. Gas-and-steam emission were detected on 6 and 17 February and 17 and 21 March.

Figure (see Caption) Figure 100. Sentinel-2 thermal satellite imagery detected thermal anomalies (bright yellow-orange) mostly visible within the Arenas crater at Nevado del Ruiz during the last three months of 2019 and were accompanied by gas-and-steam emissions. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

The number of ash emissions detected in satellite imagery increased after March, occurring on 4, 7, 16, 17-19, and 23-26 April and 2 and 4-5 May. Ash plumes were detected on 27 June, 4, 7, 8, and 29 July, 1 August, and on 19, 29, and 30 September. Los Nevados National Natural Park (PNNN) personnel reported that the ash plume on 8 July was accompanied by gas-and-steam emissions and a continuous tremor occurring at 0722 (figure 101). These emissions rose 450 m above the crater and drifted W. On 29 September, a tremor associated with an ash plume occurred at 2353. The ash plume rose to a maximum altitude of 8.5 km drifted NW, resulting in ashfall confirmed by PNNN, GOES-EAST satellite imagery, and SGC personnel in the field.

Seismicity increased during the week of 1 October compared to the previous week, which was accompanied by several gas-and-steam and ash emissions rising 1 km altitude drifting NW observed by webcams, PNNN personnel, and GOES-EAST satellite imagery. An ash plume rising 7 km altitude drifting NW on 4 October resulted in fine ashfall in Manizales. Ash plumes rose to an altitude of 7.3 km drifting N on 5, 9, and 16 October and was seen in the GOES-EAST satellite according to Washington VAAC notices. Ash emissions were observed frequently during November; 11 Washington VAAC notices, the most for any month during 2019, reported emissions ranging 5.8 to 7 km altitude drifting in different directions. Gas-and-steam plumes rose to a maximum of 2.4 km above the crater during 14 and 30 November. The number of reported emissions decreased during December with one ash emission observed on 4 December.

Figure (see Caption) Figure 101. Webcam images of gas-and-steam and ash plumes rising from Nevado del Ruiz during 2019. Courtesy of Servicio Geologico Colombiano.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


Erebus (Antarctica) — January 2020 Citation iconCite this Report

Erebus

Antarctica

77.53°S, 167.17°E; summit elev. 3794 m

All times are local (unless otherwise noted)


Lava lakes persist through 2019

Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Antarctica's Ross Island, 35 km SSW. Because of the remoteness of the volcano, activity is primarily monitored using satellites (figure 27), including MODIS infrared detectors aboard the Aqua and Terra satellites and analyzed using the MODVOLC algorithm.

Figure (see Caption) Figure 27. Satellite image of Erebus (on left) acquired on 19 October 2019 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. The false-color combines visible and near-infrared wavelengths of light (ASTER bands 3, 2, 1). The area was just days away from constant 24-hour sunlight when this image was acquired, with the Sun angle low enough to cast a long shadow towards the west. The blue patches are areas clear of surface snow, exposing glacial ice. Nearby areas that appear smooth are the snow- and ice-topped waters of McMurdo Sound. Courtesy of NASA Earth Observatory: image by Joshua Stevens, using data from NASA/METI/AIST/Japan Space Systems and U.S./Japan ASTER Science Team; description by Kathryn Hansen.

Available since 2000, MODIS-MODVOLC data have shown a strong and nearly continuous thermal signal through 2019. A compilation of thermal alert pixels during 2017-2019 (table 5, continuing the table in BGVN 44:01) shows a wide range of detected activity in 2019, with a high of 162 in April. Infrared satellite imagery from Sentinel-2 identified one or two lava lakes during January-March and September-December 2019; a few of the images showed gas emissions, possibly from melted snow (figure 28).

Table 5. Number of monthly MODVOLC thermal alert pixels recorded at Erebus from 1 January 2017 to 31 December. Table compiled using data provided by the Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System.

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec SUM
2017 0 21 9 0 0 1 11 61 76 52 0 3 234
2018 0 21 58 182 55 17 137 172 103 29 0 0 774
2019 2 21 162 151 55 56 75 53 29 19 1 0 624
Figure (see Caption) Figures 28. Sentinel-2 satellite image of Erebus in color infrared (bands 8, 4, 3) on 20 October 2019 showing two lava lakes in the summit crater. Courtesy of Sentinel Hub Playground.

Geologic Background. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. It is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. A summit plateau at about 3,200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater; other lava lakes are sometimes present. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity with minor explosions, punctuated by occasional larger Strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history.

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/).


Sangay (Ecuador) — January 2020 Citation iconCite this Report

Sangay

Ecuador

2.005°S, 78.341°W; summit elev. 5286 m

All times are local (unless otherwise noted)


Continuing ash emissions, lava flows, pyroclastic flows, and lahars through December 2019

Frequent activity at Ecuador's Sangay has included pyroclastic flows, lava flows, ash plumes, and lahars since 1628. Its remoteness on the east side of the Andean crest has made ground observations difficult until recent times. The current eruption began in March 2019; this report covers ongoing activity from July through December 2019. Information is provided by Ecuador's Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), and a number of sources of remote data including the Washington Volcanic Ash Advisory Center (VAAC), the Italian MIROVA Volcano HotSpot Detection System, and Sentinel-2 satellite imagery.

The eruption that began in March 2019 continued during July-December 2019 with activity focused on two eruptive centers at the summit, the Cráter Central and the Ñuñurco (southeast) vent. The Cráter Central produced explosive activity which generated small ash emissions that rose up to 3.2 km above the crater and were frequently directed towards the W and SW. Associated with these emissions in early November, ashfall was reported in Chimborazo province and elsewhere, and ejecta from explosions was deposited on all the upper flanks. At the Ñuñurcu vent, effusive activity resulted in an almost continuous emission of material down the SE flank. Small rockfalls and pyroclastic flows along the fronts and sides of the flows reached the basin and upper channel of the Volcán river which flows into the Upano river. These deposits were remobilized by rainfall and formed mud and debris flows (lahars) in the Volcán river, which caused damming at the confluence with the Upano river downstream. Increased thermal activity was recorded by the MIROVA system from mid-May 2019 through the end of the year, corresponding to the ongoing lava flow and explosive activity (figure 36).

Figure (see Caption) Figure 36. Increased heat flow at Sangay was recorded beginning in mid-May 2019 and continued steadily through the end of the year as seen in this graph of Log Radiative Power produced by the MIROVA project. Courtesy of MIROVA.

Activity during July-September 2019. Several ash emissions were reported by the Washington VAAC during the first part of July 2019. On 1 July a plume rose to 6.7 km altitude and extended 45 km WSW from the summit. During 3-4 July a plume rose 6.4 km and drifted WNW; it included occasional discrete emissions that extended approximately 35 km from summit. The VAAC recorded a bright hotspot in SWIR imagery on 4 July. On 11 July a 7.3-km-altitude ash plume detached from the summit and extended from immediately W of the summit S past Segu. Webcam and satellite imagery on 11 July demonstrated the continuing thermal activity of the lava flow on the SE flank and ash emissions drifting W (figure 37). On 29 July a plume rose to 7.6 km altitude and drifted 65 km WSW. Later in the day continuous emissions were drifting SW from the summit at 5.8 km altitude before dissipating. The first satellite images of 30 July showed a plume extending 110 km WSW from the summit at 7 km altitude. Activity decreased later in the day and the plume extended W about 45 km from the summit at 6.4 km altitude. Composite satellite imagery on 31 July showed almost constant ash emissions extending over 150 km W of the summit (figure 38).

Figure (see Caption) Figure 37. The local webcam at Sangay (left) and Sentinel satellite imagery (right, bands 12, 11, and 8A) both confirmed the high heat output from the active lava flow on the SE flank on 11 July 2019. The flow is about 2 km long. A plume of steam and ash also drifted W from the summit (right). Courtesy of IG-EPN (left) and Sentinel Hub Playground (right).
Figure (see Caption) Figure 38. An ash emission from Sangay on 29 July 2019 drifted tens of km WSW as seen in the webcam (left). Two days later on 31 July a small dark ash plume was visible above the dense cloud cover in Sentinel satellite imagery; the VAAC reported ash drifting W throughout the day. Courtesy of IG-EPN (left) and Sentinel Hub Playground (right).

During an overflight on 6 August 2019 scientists from IG-EPN observed ash emissions from the Cráter Central, and the lava flow continuing from the Vento Ñuñurco in a similar location to where it was in May 2019 (figure 39). Light-colored sediments filled much of the upper basin of the Volcán river. Thermal images of the area also showed that some of the deposits were elevated in temperature, even in the riverbed (figure 40).

Figure (see Caption) Figure 39. The E and SE flanks of Sangay showed continuing activity during August 2019 (right) that was similar to activity going on during May (left). In May, steam issued from the Cráter Central and a lava flow descended the SE flank from Vento Ñuñurco (photo by M. Almeida, IG-EPN). In August, diffuse ash and steam issued from the Crater Central, and a new flow descended from the same area of the Vento Ñuñurco seen in May (photo by P. Ramón , IG-EPN). Courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 5, Quito, 13 de noviembre del 2019).
Figure (see Caption) Figure 40. The upper Volcán River basin was filled with deposits of pyroclastic material associated with the most recent activity at Sangay when observed during an overflight on 6 August 2019 (left). Thermal analysis of the drainage indicated that several of the deposits were still hot, as was the active flow (right). Left photo by P. Ramón, thermal image by Silvia Vallejo; courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 5, Quito, 13 de noviembre del 2019).

Frequent ash emissions continued during August 2019. Diffuse ash was seen moving W from the summit at 5.8 km altitude on 1 August. Another short-lived plume was observed extending 15 km WSW the next day at 5.8-6.1 km altitude. Continuous ash emissions were visible in satellite imagery extending 35 km SW from the summit at 6.1 km altitude on 5 August. During the next two days, the emissions extended 45 km WSW and a prominent hot spot was visible through the meteoric clouds. The ash plume altitude rose to 6.7 km on 8 August and a larger ash emission extended more than 100 km WSW. A new emission the next day drifted 25-35 km W at 6.1 km altitude. A well-defined hotspot seen in shortwave imagery on 10 August accompanied an ash emission that extended 35 km WSW from the summit at 6.7 km altitude. On 12 August a plume drifted 65 km due W at 6.4 km altitude; emissions continued the next day in the same direction at 6.1 km altitude. An ash plume extended 100 km WNW of the summit at 5.8 km altitude on 18 August. A very bright hotspot was observed in infrared imagery the next day. The ash emissions continued to be visible in satellite imagery through 20 August.

An ash plume extending 10 km N from the summit on 25 August coincided with the appearance of a vivid hot spot, according to the Washington VAAC. The plume was initially reported at 7.6 km altitude and later in the day was at 6.7 km altitude. The leading edge of an ash emission reported on 31 August was 350 km W of the summit late that day moving at 5.8 km altitude, and over 950 km WSW before it dissipated on 1 September. Fewer ash emissions were reported during September 2019. The leading edge of a plume extended about 160 km W from the summit on 2 September at 7.6 km altitude; a second emission that day moved NE at 6.4 km altitude. On 4 September a small emission rose to 6.4 km altitude and drifted SW; on 9 September a plume was observed moving W at 5.5 km. A new emission on 19 September was seen in satellite imagery moving in many different directions (N, NE, E, and SE) at 6.7 km altitude. The lava flow on the SE flank produced a strong thermal signature that appeared unchanged from late August through late September (figure 41).

Figure (see Caption) Figure 41. The thermal signature from the lava flow on the SE flank of Sangay appeared unchanged from late August (top left) to late September 2019 (bottom right) in Sentinel-2 imagery (bands 12, 11, and 8A); an ash emission drifted in multiple directions on 19 September 2019. Courtesy of Sentinel Hub Playground and IG-EPN.

Activity during October-December 2019. Pulses of ash were reported during 1, 9-11, 14, 26, and 31 October 2019 by the Washington VAAC. On 1 October the plume rose to 5.8 km altitude and drifted NE. A narrow plume on 9 October extending 55 km NW corresponded with a bright hotspot at its source. Concentrated emissions the next day rose to 7.3 km altitude and extended over 200 km WNW. Later in the day on 10 October emissions were reported at 5.8 km drifting W. A substantial thermal anomaly and a constant plume of diffuse ash appeared in satellite imagery on 14 October at 6.1 km altitude drifting 15 km W. Diffuse emissions on 26 October appeared 35 km NW of the summit at 5.8 km altitude. The intensity of the thermal anomaly from the lava flow on the SE flank remained strong during the month, and emissions of steam and ash were also visible in satellite images (figure 42). In a site visit on 19 October 2019, IG-EPN scientists measured a recent lahar deposited near the confluence of the Volcán and Upano rivers. It was full of sand-sized particles and approximately 30 cm thick at the river’s edge (figure 43).

Figure (see Caption) Figure 42. The thermal anomaly from the lava flow on the SE flank of Sangay remained strong during October 2019, and both ash and steam emissions were seen in Sentinel-2 satellite images (bands 12, 11, and 8A). The lava flow is about 2 km long. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 43. A lahar deposit at the confluence of Río Volcán and Río Upano at Sangay was about 30 cm thick on 19 October 2019. Photograph by Francisco Vasconez, courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 5, Quito, 13 de noviembre del 2019).

Ash emissions during 10-26 November 2019 were reported daily by the Washington VAAC, each lasting for less than 24 hours before dissipating. The first report of ash detected in satellite imagery on 10 November indicated that the plume extended 25 km WSW at 6.7 km altitude. On the subsequent days, the plumes drifted in many different directions at altitudes of 5.8-7.3 km, usually around 6.4 km. The plumes generally drifted 25-45 km from the summit, although some were still visible over 100 km away, depending on weather conditions. The highest plume reached 7.3 km altitude on 18 November and drifted W. The plume on 26 November rose to 6.4 km altitude and was last seen 140 km SW of the summit before it dissipated. Pyroclastic flows were witnessed on 20 November 2019 (figure 44). The last plume of the month, on 29 November, rose to 6.4 km altitude and drifted 65 km W, dissipating quickly, and was accompanied by a very bright thermal anomaly.

Figure (see Caption) Figure 44. Ash plumes from Sangay rose to 5.8 km altitude on 20 November 2019 and drifted 25 km NE before dissipating, according to the Washington VAAC. Pyroclastic flows appeared on the flank that day. Courtesy of Walter Calle C.

Ashfall was reported during November in the provinces of Chimborazo (Alao, 20 km NW, Cebadas, 35 km NW, and Guaguallá), Morona Santiago (Macas, 40 km SE), and Azuay (120 km SW). Samples of ash collected from two locations indicated that the amount of material was very small (less than10 g/m2) with a high content of extremely fine ash (between 40 and 60% ash less 63 μm in diameter). The larger fraction over 63 μm was mainly composed of juvenile magma (80%) and a small fraction of free crystals (10% plagioclase and pyroxenes), oxidized fragments (5%), and gray lithics (5%) (figure 45).

Figure (see Caption) Figure 45. Photos from a binocular microscope of the greater than 63 μm fraction of ash from Sangay collected in Macas and at the SAGA station during November 2019. See text for details. Courtesy if IG (Informe Especial del Volcán Sangay - 2019 - No 6, 4 de diciembre del 2019).

In a report issued in early December 2019 the IG-EPN noted that eruptive activity which increased in May 2019 was continuing (figure 46); a small amount of inflation was observed during November. Explosive activity continued at the Cráter Central with ash plumes reaching 2 km above the summit, and plumes drifting frequently towards the NE causing small amounts of ash to fall in the Chimborazo, Morona Santiago, and Azuay provinces. Effusive activity from the Ñuñurco vent produced almost continuous lava that flowed down the SE flank. Small pyroclastic flows around the margins of the lava flows reached the basin and the upper channel of the Volcán river, causing temporary dams that turned to mudflows during rain events.

Figure (see Caption) Figure 46. IG-EPN published this multi-parameter chart of activity of the Sangay volcano from May to 1 December 2019. a: seismic activity (number of events per day) detected at the PUYO station (source: IG-EPN); b: SO2 emissions (tons per day) detected by the Sentinel-5P satellite sensor (source: MOUNTS); c: height of ash clouds (m above crater level) detected by the GOES-16 satellite sensor (source: Washington VAAC); d: thermal emission power (megawatt) detected by the MODIS satellite sensor (source: MODVOLC) and estimated accumulated lava volume (million m3, dotted lines represent the error range). Courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 6, 4 de diciembre del 2019).

During an overflight on 3 December 2019 a strong smell of sulfur was noted 1 km above the summit. The Ñuñurco vent continued to emit lava with a maximum apparent temperature of 100 to 210°C (figure 47). IG-EPN scientists concluded that approximately 58 ± 29 million m3 of lava had been emitted through 3 December.

Figure (see Caption) Figure 47. Views of the SE flank of Sangay on 3 December 2019 with visible (left) and thermal (right) imagery. Photograph by C. Viracucha, thermal analysis by F. Naranjo; courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 6, 4 de diciembre del 2019).

Recurring lahars in the Río Volcán during the period occasionally reached the Rio Upano (figure 48). By late November, they had partially dammed the Upano river (figure 49). On 26 November 2019 when IG-EPN and Sangay National Park officials inspected the area, they recorded deposits more than 2 m thick at the confluence of the two rivers (figure 50). During an overflight the next day, additional deposits were identified along 16 km upstream. The total volume of the lahar deposits was estimated at 5 million m3 to date.

Figure (see Caption) Figure 48. Inferred lahar deposits at Sangay along the Río Volcán from the foot of the volcano up to its confluence with Río Upano shown in red. Courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 6, 4 de diciembre del 2019).
Figure (see Caption) Figure 49. Lahar deposits at Sangay filled Río Volcán and dammed part of the confluence where it joins río Upano when photographed during an overflight on 26 November 2019. Photographs by Pedro Espín; courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 6, 4 de diciembre del 2019).
Figure (see Caption) Figure 50. Lahar deposits from Sangay exceeded 2 m in thickness at the confluence of the Upano and Volcán rivers on 26 November 2019. Photography by Pedro Espín; courtesy of IG-EPN (Informe Especial del Volcán Sangay - 2019 - No 6, 4 de diciembre del 2019).

Another extended period of ash emissions began on 4 December 2019 and continued daily through 19 December. The Washington VAAC reported that an ash plume was initially at 6.7 km altitude drifting S on 4 December. Continuous emissions were observed at 4.6 km altitude later in the day and were visible in satellite images located 25 km S at 5.8 km altitude that evening. The drift directions were initially mostly SW in early December, but migrated to mostly SE during 10-16 December, then back to SW. Plume altitudes ranged from 5.8 to 7.3 km and satellite images revealed ash as far as 160 km away; most plumes were visible to about 25 km before dissipating or disappearing into meteoric clouds. IG-EPN reported steam and gas emissions with small amounts of ash on 13 December that drifted SE (figure 51). Small block avalanches from the active flow were also observed on the SE flank. The next day, ash and gas emissions rose to 1,170 m above the summit and drifted NE while the lava flow appeared incandescent on the SE flank.

During the night of 14-15 December ashfall was reported in San Isidro in the Province of Morona Santiago (30 km SE). Ash plumes rose 870 m above the summit on 15 December and 1,470 m high the next day. Ashfall was reported in the Guasuntos (60 km SW) and Llagos (80 km SW) areas of the Chimborazo province on the morning of 16 December. The next day plumes drifted SE and SW, and minor ashfall was reported that night (16-17 December) in Macas (40 km SE), Morona Santiago province. Satellite images captured gas and ash emissions on 25 December, and ashfall was reported in Alausí (60 km SW) in the province of Chimborazo. An explosion on 29 December produced an ash plume that rose to 6.1 km and first drifted WNW then in an arc to the SW almost 185 km to the coast. Multiple plumes at 5.8-6.7 km drifted westerly for tens of kilometers that day and the next. Prominent thermal anomalies were noted in satellite imagery on 8, 15, 17, and 30 December.

Figure (see Caption) Figure 51. Numerous explosions produced ash emissions from Sangay during 4-30 December 2019, shown here on days 13, 14, 16, and 25. Courtesy of IG-EPN (Informe Diario del Estado del Volcán Sangay No. 2019-1, 13 Diciembre; No. 2019-2, 14 Diciembre; No. 2019-5, 17 Diciembre; No. 2019-13, 25 Diciembre 2019).

By late December 2019, the lahar deposits in Rio Volcán had backed up noticeably further into the Upano river from a month earlier (figure 52). Sulfur dioxide emissions were not recorded during July through August 2019, but small, pulsing plumes were captured in satellite images during September, October and November, gradually increasing in density. Several plumes were detected hundreds of kilometers from the volcano before dissipating; by December, larger, more frequent pulses of SO2 were measured during many days when ash emissions were reported (figure 53).

Figure (see Caption) Figure 52. Lahar deposits from Sangay in the Rio Volcán (right) continued to dam up the Rio Upano into late December 2019. Compare with figure 49 taken one month earlier. Photo by WJ Hernandes, courtesy of Edgar Chulde, posted online 21 December 2019.
Figure (see Caption) Figure 53. Sulfur dioxide emissions from Sangay were weak but persistent during September-November 2019 (top row), often drifting in narrow plumes with distinct pulses. During December, the density of the SO2 emissions increased noticeably (bottom row). Columbia’s Nevado del Ruiz was also producing plumes of SO2 at the same time. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Information Contacts: Instituto Geofísico (IG-EPN), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Walter Calle C., Macas, Ecuador (Twitter: @walterc333; URL: https://twitter.com/walterc333/status/1197273200822046720); Edgar Chulde, Quito, Ecuador (Twitter: @EdgarChulde2; URL: https://twitter.com/EdgarChulde2/status/1208547471024173056).


Shishaldin (United States) — February 2020 Citation iconCite this Report

Shishaldin

United States

54.756°N, 163.97°W; summit elev. 2857 m

All times are local (unless otherwise noted)


Multiple lava flows, pyroclastic flows, lahars, and ashfall events during October 2019 through January 2020

Shishaldin is located near the center of Unimak Island in Alaska and has been frequently active in recent times. Activity includes steam plumes, ash plumes, lava flows, lava fountaining, pyroclastic flows, and lahars. The current eruption phase began on 23 July 2019 and through September included lava fountaining, explosions, and a lava lake in the summit crater. Continuing activity during October 2019 through January 2020 is described in this report based largely on Alaska Volcano Observatory (AVO) reports, photographs, and satellite data.

Minor steam emissions were observed on 30 September 2019, but no activity was observed through the following week. Activity at that time was slightly above background levels with the Volcano Alert Level at Advisory and the Aviation Color Code at Yellow (figure 17). In the first few days of October weak tremor continued but no eruptive activity was observed. Weakly elevated temperatures were noted in clear satellite images during 4-9 October and weak tremor continued. Elevated temperatures were recorded again on the 14th with low-level tremor.

Figure (see Caption) Figure 17. Alaska Volcano Observatory hazard status definitions for Aviation Color Codes and Volcanic Activity Alert Levels used for Shishaldin and other volcanoes in Alaska. Courtesy of AVO.

New lava extrusion was observed on 13 October, prompting AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch. Elevated surface temperatures were detected by satellite during the 13th and 17-20th, and a steam plume was observed on the 19th. A change from small explosions to continuous tremor that morning suggested a change in eruptive behavior. Low-level Strombolian activity was observed during 21-22 October, accompanied by a persistent steam plume. Lava had filled the crater by the 23rd and began to overflow at two places. One lava flow to the north reached a distance of 200 m on the 24th and melted snow to form a 2.9-km-long lahar down the N flank. The second smaller lava flow resulted in a 1-km-long lahar down the NE flank. Additional snowmelt was produced by spatter accumulating around the crater rim. By 25 October the northern flow reached 800 m, there was minor explosive activity with periodic lava fountaining, and lahar deposits reached 3 km to the NW with shorter lahars to the N and E (figure 18). Trace amounts of ashfall extended at least 8.5 km SE. There was a pause in activity on the 29th, but beginning at 1839 on the 31st seismic and infrasound monitoring detected multiple small explosions.

Figure (see Caption) Figure 18. PlanetScope satellite images of Shishaldin on 3 and 29 October 2019 show the summit crater and N flank before and after emplacement of lava flows, lahars, and ashfall. Copyright PlanetLabs 2019.

Elevated activity continued through November with multiple lava flows on the northern flanks (figure 19). By 1 November the two lava flows had stalled after extending 1.8 km down the NW flank. Lahars had reached at least 4 km NW and trace amounts of ash were deposited on the north flank. Elevated seismicity on 2 November indicated that lava was likely flowing beyond the summit crater, supported by a local pilot observation. The next day an active lava flow moved 400 m down the NW flank while a smaller flow was active SE of the summit. Minor explosive activity and/or lava fountaining at the summit was indicated by incandescence during the night. Small explosions were recorded in seismic and infrasound data. On 5 November the longer lava flow had developed two lobes, reaching 1 km in length. The lahars had also increased in length, reaching 2 km on the N and S flanks. Incandescence continued and hot spatter was accumulating around the summit vent. Activity continued, other than a 10-hour pause on 4-5 November, and another pause on the 7th. The lava flow length had reached 1.3 km on the 8th and lahar deposits reached 5 km.

Figure (see Caption) Figure 19. Sentinel-2 thermal satellite images show multiple lava flows (orange) on the upper northern flanks of Shishaldin between 1 November and 1 December 2019. Blue is snow and ice in these images, and partial cloud cover is visible in all of them. Sentinel-2 Urban rendering (bands 21, 11, 4) courtesy of Sentinel Hub Playground.

After variable levels of activity for a few days, there was a significant increase on 10-11 November with lava fountaining through the evening and night. This was accompanied by minor to moderate ash emissions up to around 3.7 km altitude and drifting northwards, and a significant increase in seismicity. Activity decreased again during the 11-12th while minor steam and ash emissions continued. On 14 November minor ash plumes were visible on the flanks, likely caused by the collapse of accumulated spatter. By 15 November a large network of debris flows consisting of snowmelt and fresh deposits extended 5.5 km NE and the collapse of spatter mounds continued. Ashfall from ash plumes reaching as high as 3.7 km altitude produced thin deposits to the NE, S, and SE. Activity paused during the 17-18th and resumed again on the 19th; intermittent clear views showed either a lava flow or lahar descending the SE flank. Activity sharply declined at 0340 on the 20th.

Seismicity began increasing again on 24 November and small explosions were detected on the 23rd. A small collapse of spatter that had accumulated at the summit occurred at 2330 on the 24th, producing a pyroclastic flow that reached 3 km in length down the NW flank. A new lava flow had also reached several hundred meters down the same flank. Variable but elevated activity continued over 27 November into early December, with a 1.5-km-long lava flow observed in satellite imagery acquired on the 1st. On 5 December minor steam or ash emissions were observed at the summit and on the north flank, and Strombolian explosions were detected. Activity from that day produced fresh ash deposits on the northern side of the volcano and a new lava flow extended 1.4 km down the NW flank. Three small explosions were detected on the 11th.

At 0710 on 12 December a 3-minute-long explosion produced an ash plume up to 6-7.6 km altitude that dispersed predominantly towards the W to NW and three lightning strokes were detected. Ash samples were collected on the SE flank by AVO field crews on 20 December and analysis showed variable crystal contents in a glassy matrix (figure 20). A new ash deposit was emplaced out to 10 km SE, and a 3.5-km-long pyroclastic flow had been emplaced to the north, containing blocks as large as 3 m in diameter. The pyroclastic flow was likely a result from collapse of the summit spatter cone and lava flows. A new narrow lava flow had reached 3 km to the NW and lahars continued out to the northern coast of Unimak island (figure 21). The incandescent lava flow was visible from Cold Bay on the evening of the 12th and a thick steam plume continued through the next day.

Figure (see Caption) Figure 20. An example of a volcanic ash grain that was erupted at Shishaldin on 12 December 2019 and collected on the SE flank by the Alaska Volcano Observatory staff. This Scanning Electron Microscope images shows the different crystals represented by different colors: dark gray crystals are plagioclase, the light gray crystals are olivine, and the white ones are Fe-Ti oxides. The groundmass in this grain is nearly completely crystallized. Courtesy of AVO.
Figure (see Caption) Figure 21. A WorldView-2 satellite image of Shishaldin with the summit vent and eruption deposits on 12 December 2019. The tephra deposit extends around 10 km SE, a new lava flow reaching 3 km NW with lahars continuing to the N coast of Unimak island. Pyroclastic flow deposits reach 3.5 km to the N and contain blocks as large as 3 m. Courtesy of Hannah Dietterich, AVO.

A new lava flow was reported by a pilot on the night of 16 December. Thermal satellite data showed that this flow reached 2 km to the NW. High-resolution radar satellite images over the 15-17th showed that the lava flow had advanced out to 2.5 km and had developed levees along the margins (figure 22). The lava channel was 5-15 m wide and was originating from a crater at the base of the summit scoria cone, which had been rebuilt since the collapse the previous week. Minor ash emissions drifted to the south on the 19tt and 20th (figure 23).

Figure (see Caption) Figure 22. TerraSAR-X radar satellite images of Shishaldin on 15 and 17 December 2019 show the new lava flow on the NW flank and growth of a scoria cone at the summit. The lava flow had reached around 2.5 km at this point and was 5-15 m wide with levees visible along the flow margins. Pyroclastic flow deposits from a scoria cone collapse event on 12 December are on the N flank. Figure courtesy of Simon Plank (German Aerospace Center, DLR) and Hannah Dietterich (AVO).
Figure (see Caption) Figure 23. Geologist Janet Schaefer (AVO/DGGS) collects ash samples within ice and snow on the southern flanks of Shishaldin on 20 December 2019. A weak ash plume is rising from the summit crater. Photo courtesy of Wyatt Mayo, AVO.

On 21 December a new lava flow commenced, traveling down the northern slope and accompanied by minor ash emissions. Continued lava extrusion was indicated by thermal data on the 25th and two lava flows reaching 1.5 km and 100 m were observed in satellite data on the 26th, as well as ash deposits on the upper flanks (figure 24). Weak explosions were detected by the regional infrasound network the following day. A satellite image acquired on the 30th showed a thick steam plume obscuring the summit and snow cover on the flanks indicating a pause in ash emissions.

Figure (see Caption) Figure 24. This 26 December 2019 WorldView-2 satellite image with a close-up of the Shishaldin summit area to the right shows a lava flow extending nearly 1.5 km down the NW flank and a smaller 100-m-long lava flow to the NE. Volcanic ash was deposited around the summit, coating snow and ice. Courtesy of Matt Loewen, AVO.

In early January satellite data indicated slow lava extrusion or cooling lava flows (or both) near the summit. On the morning of the 3rd an ash plume rose to 6-7 km altitude and drifted 120 km E to SE, producing minor amounts of volcanic lightning. Elevated surface temperatures the previous week indicated continued lava extrusion. A satellite image acquired on 3 January showed lava flows extending to 1.6 km NW, pyroclastic flows moving 2.6 km down the western and southern flanks, and ashfall on the flanks (figure 25).

Figure (see Caption) Figure 25. This WorldView-2 multispectral satellite image of Shishaldin, acquired on 3 January 2019, shows the lava flows reaching 1.6 km down the NW flank and an ash plume erupting from the summit dispersing to the SE. Ash deposits cover snow on the flanks. Courtesy of Hannah Dietterich, AVO.

On 7 January the most sustained explosive episode for this eruption period occurred. An ash plume rose to 7 km altitude at 0500 and drifted east to northeast then intensified reaching 7.6 km altitude with increased ash content, prompting an increase of the Aviation Color Code to Red and Volcano Alert Level to Warning. The plume traveled over 200 km to the E to NE (figure 26). Lava flows were produced on the northern flanks and trace amounts of ashfall was reported in communities to the NE, resulting in several flight cancellations. Thermal satellite images showed active lava flows extruding from the summit vent (figure 27). Seismicity significantly decreased around 1200 and the alert levels were lowered to Orange and Watch that evening. Through the following week no notable eruptive activity occurred. An intermittent steam plume was observed in webcam views.

Figure (see Caption) Figure 26. This Landsat 8 satellite image shows a detached ash plume drifts to the NE from an explosive eruption at Shishaldin on 7 January 2020. Courtesy of Chris Waythomas, AVO.
Figure (see Caption) Figure 27. This 7 January 2019 Sentinel-2 thermal satellite image shows several lava flows on the NE and NW flanks of Shishaldin, as well as a steam plume from the summit dispersing to the NE. Blue is snow and ice in this false color image (bands 12, 11, 4). Courtesy of Sentinel-Hub playground.

Eruptive activity resumed on 18 January with lava flows traveling 2 km down the NE flank accompanied by a weak plume with possible ash content dispersing to the SW (figure 28). A steam plume was produced at the front of the lava flow and lahar deposits continued to the north (figures 29 to 32). Activity intensified from 0030 on the 19th, generating a more ash-rich plume that extended over 150 km E and SE and reached up to 6 km altitude; activity increased again at around 1500 with ash emissions reaching 9 km altitude. AVO increased the alert levels to Red/Warning. Lava flows traveled down the NE and N flanks producing meltwater lahars, accompanied by elevated seismicity (figures 33). Activity continued through the day and trace amounts of ashfall were reported in False Pass (figure 34). Activity declined to small explosions over the next few days and the alert levels were lowered to Orange/watch shortly after midnight. The next morning weak steam emissions were observed at the summit and there was a thin ash deposit across the entire area. Satellite data acquired on 23 January showed pyroclastic flow deposits and cooling lava flows on the northern flank, and meltwater reaching the northern coast (figure 35).

Figure (see Caption) Figure 28. This Worldview-3 multispectral near-infrared satellite image acquired on 18 January 2020 shows a lava flow down the NE flank of Shishaldin. A steam plume rises from the end of the flow and lahar deposits from snowmelt travel further north. Courtesy of Matt Loewen, AVO.
Figure (see Caption) Figure 29. Steam plumes from the summit of Shishaldin and from the lava flow down the NE flank on 18 January 2020. Lahar deposits extend from the lava flow front and towards the north. Photo courtesy of Matt Brekke, via AVO.
Figure (see Caption) Figure 30. A lava flow traveling down the NE flank of Shishaldin on 18 January 2020, seen from Cold Bay. Photo courtesy of Aaron Merculief, via AVO.
Figure (see Caption) Figure 31. Two plumes rise from Shishaldin on 18 January 2020, one from the summit crater and the other from the lava flow descending the NE Flank. Photos courtesy of Woodsen Saunders, via AVO.
Figure (see Caption) Figure 32. A low-altitude plume from Shishaldin on the evening of 18 January 2020, seen from King Cove. Photo courtesy of Savannah Yatchmeneff, via AVO.
Figure (see Caption) Figure 33. This WorldView-2 near-infrared satellite image shows a lava flow reaching 1.8 km down the N flank and lahar deposits filling drainages out to the Bering Sea coast (not shown here) on 19 January 2020. Ash deposits coat snow to the NE and E. Courtesy of Matt Loewen, AVO.
Figure (see Caption) Figure 34. An ash plume (top) and gas-and-steam plumes (bottom) at Shishaldin on 19 January 2020. Courtesy of Matt Brekke, via AVO.
Figure (see Caption) Figure 35. A Landsat 8 thermal satellite image (band 11) acquired on 23 January 2019 showing hot lava flows and pyroclastic flow deposits on the flanks of Shishaldin and the meltwater flow path to the Bering Sea. Figure courtesy of Christ Waythomas, AVO.

Activity remained low in late January with some ash resuspension (due to winds) near the summit and continued elevated temperatures. Seismicity remained above background levels. Infrasound data indicated minor explosive activity during 22-23 January and small steam plumes were visible on 22, 23, and 26 January. MIROVA thermal data showed the rapid reduction in activity following activity in late-January (figure 36).

Figure (see Caption) Figure 36. MIROVA thermal data showing increased activity at Shishaldin during August-September, and an even higher thermal output during late-October 2019 to late January 2020. Courtesy of MIROVA.

Geologic Background. The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/); Simon Plank, German Aerospace Center (DLR) German Remote Sensing Data Center, Geo-Risks and Civil Security, Oberpfaffenhofen, 82234 Weßling (URL: https://www.dlr.de/eoc/en/desktopdefault.aspx/tabid-5242/8788_read-28554/sortby-lastname/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Planet Labs, Inc. (URL: https://www.planet.com/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Sangeang Api (Indonesia) — February 2020 Citation iconCite this Report

Sangeang Api

Indonesia

8.2°S, 119.07°E; summit elev. 1912 m

All times are local (unless otherwise noted)


Ash emissions and lava flow extrusion continue during May 2019 through January 2020

Sangeang Api is located in the eastern Sunda-Banda Arc in Indonesia, forming a small island in the Flores Strait, north of the eastern side of West Nusa Tenggara. It has been frequently active in recent times with documented eruptions spanning back to 1512. The edifice has two peaks – the active Doro Api cone and the inactive Doro Mantori within an older caldera (figure 37). The current activity is focused at the summit of the cone within a horseshoe-shaped crater at the summit of Doro Api. This bulletin summarizes activity during May 2019 through January 2020 and is based on Darwin Volcanic Ash Advisory Center (VAAC) reports, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, or CVGHM) MAGMA Indonesia Volcano Observatory Notice for Aviation (VONA) reports, and various satellite data.

Figure (see Caption) Figure 37. A PlanetScope satellite image of Sangeang Api with the active Doro Api and the inactive Doro Mantori cones indicated, and the channel SE of the active area that contains recent lava flows and other deposits. December 2019 monthly mosaic copyright of Planet Labs 2019.

Thermal anomalies were visible in Sentinel-2 satellite thermal images on 4 and 5 May with some ash and gas emission visible; bright pixels from the summit of the active cone extended to the SE towards the end of the month, indicating an active lava flow (figure 38). Multiple small emissions with increasing ash content reached 1.2-2.1 km altitude on 17 June. The emissions drifted W and WNW, and a thermal anomaly was also visible. On the 27th ash plumes rose to 2.1 km and drifted NW and the thermal anomaly persisted. One ash plume reached 2.4 km and drifted NW on the 29th, and steam emissions were ongoing. Satellite images showed two active lava flows in June, an upper and a lower flow, with several lobes descending the same channel and with lateral levees visible in satellite imagery (figure 39). The lava extrusion appeared to have ceased by late June with lower temperatures detected in Sentinel-2 thermal data.

Figure (see Caption) Figure 38. Sentinel-2 satellite thermal images of Sangeang Api on 20 May and 9 June 2019 show an active lava flow from the summit, traveling to the SE. False color (urban) image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 39. PlanetScope satellite images of Sangeang Api show new lava flows during June and July, with white arrows indicating the flow fronts. Copyright Planet Labs 2019.

During 4-5 July the Darwin VAAC reported ash plumes reaching 2.1-2.3 km altitude and drifting SW and W. Activity continued during 6-9 July with plumes up to 4.6 km drifting N, NW, and SW. Thermal anomalies were noted on the 4th and 8th. Plumes rose to 2.1-3 km during 10-16th, and to a maximum altitude of 4.6 km during 17-18 and 20-22. Similar activity was reported during 24-30 July with plumes reaching 2.4-3 km and dispersing NW, W, and SW. The upper lava flow had increased in length since 15 June (see figure 39).

During 31 July through 3 September ash plumes continued to reach 2.4-3 km altitude and disperse in multiple directions. Similar activity was reported throughout September. Thermal anomalies also persisted through July-September, with evidence of hot avalanches in Sentinel-2 thermal satellite imagery on 23 August, and 9, 12, 22, and 27 September. Thermal anomalies suggested hot avalanches or lava flows during October (figure 40). During 26-28 October short-lived ash plumes were reported to 2.1-2.7 km above sea level and dissipated to the NW, WNW, and W. Short-lived explosions produced ash plumes up to 2.7-3.5 km altitude were noted during 30-31 October and 3-4 November 2019.

Figure (see Caption) Figure 40. Sentinel-2 satellite thermal images of Sangeang Api on 7 and 22 October 2019 show an area of elevated temperatures trending from the summit of the active cone down the SE flank. False color (urban) image rendering (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Discrete explosions produced ash plumes up to 2.7-3.5 km altitude during 3-4 November, and during the 6-12th the Darwin VAAC reported short-lived ash emissions reaching 3 km altitude. Thermal anomalies were visible in satellite images during 6-8 November. A VONA was released on 14 November for an ash plume that reached about 2 km altitude and dispersed to the west. During 14-19 November the Darwin VAAC reported short-lived ash plumes reaching 2.4 km that drifted NW and W. Additional ash plumes were observed reaching a maximum altitude of 2.4 km during 20-26 November. Thermal anomalies were detected during the 18-19th, and on the 27th.

Ash plumes were recorded reaching 2.4 km during 4-5, 7-9, 11-13, and 17-19 December, and up to 3 km during 25-28 December. There were no reports of activity in early to mid-January 2020 until the Darwin VAAC reported ash reaching 3 km on 23 January. A webcam image on 15 January showed a gas plume originating from the summit. Several fires were visible on the flanks during May 2019 through January 2020, and this is seen in the MIROVA log thermal plot with the thermal anomalies greater than 5 km away from the crater (figure 41).

Figure (see Caption) Figure 41. MIROVA log plot of radiative power indicates the persistent activity at Sangeang Api during April 2019 through March 2020. There was a slight decline in September-October 2019 and again in February 2020. Courtesy of MIROVA.

Geologic Background. Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, Doro Api and Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent historical eruptions have been recorded since 1512, most of them during in the 20th century.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/).

Search Bulletin Archive by Publication Date

Select a month and year from the drop-downs and click "Show Issue" to have that issue displayed in this tab.

   

The default month and year is the latest issue available.

Bulletin of the Global Volcanism Network - Volume 40, Number 03 (March 2015)

Managing Editor: Richard Wunderman

Axial Seamount (Undersea Features)

Cabled array provides data for suspected underwater eruption in April 2015

Ontakesan (Japan)

Eruptions: (a) March 2007 and (b) 27 September 2014 (~60 deaths and ~70 injured)

Tungurahua (Ecuador)

Three periods of intense volcanism during late 2010-2011



Axial Seamount (Undersea Features) — March 2015 Citation iconCite this Report

Axial Seamount

Undersea Features

45.95°N, 130°W; summit elev. -1410 m

All times are local (unless otherwise noted)


Cabled array provides data for suspected underwater eruption in April 2015

Axial Seamount appears to have undergone an eruption starting 23-24 April 2015 Pacific Time (local time= UTC-08 hours, or Day Light Saving time, 8 March to 1 November = UTC-07 hours on the US west coast). At this time, evidence of the eruption stems from increases in seismicity, deformation, and seawater temperature around Axial, recorded in the weeks after 23 April UTC. The length of the eruption is currently unknown; however, it likely lasted days to weeks (William Chadwick, personal communication). Two expeditions to Axial are planned for this coming July and August on R/V Thompson, during which further investigation regarding the 2015 eruption will be completed (personal communication).

Axial Seamount sits along the Juan de Fuca ridge ~480 km off the coasts of Oregon and Washington (figure 1 in BGVN 23:01). Eruptions were detected seismically and geodetically in 1998 and 2011 and confirmed shortly after each eruption during submersible dives. Since about 410 AD, the volcano produced over 50 lava flows (Clague and others, 2013). On this basis, Axial is described as the NE Pacific's most active submarine volcano.

In this Bulletin report, we present information on the April 2015 eruption taken from several sources referred to in the text and provided in the Reference list near the end of this report. The sources include (a) an Oregon State University (OSU) online press release (OSU, 2015); (b) blog posts on the website of NOAA's Pacific Marine Environmental Laboratory's (PMEL) Earth-Ocean Interactions Program (EOI) (Chadwick and Nooner, 2015); (c) a post on the Networked Observations and Visualization of the Axial Environment (NOVAE) website (Delaney, 2015); and (d) seismic data posted on William Wilcock's website (Wilcock, 2015).

The last two Bulletin reports (BGVN 36:07 and 37:10) detailed Axial's previous eruption, which occurred during 6-12 April 2011 and erupted 99 x 106 m3 of lava.

Instrumentation. Since September 2014, Axial Seamount has been a part of the Ocean Observatories Initiative's (OOI) Cabled Array, which is operated by the University of Washington. As explained in their online literature (OOI, posting date uncertain1), OOI is funded by the National Science Foundation and is "an integrated infrastructure project composed of science-driven platforms and sensor systems to measure physical, chemical, geological and biological properties and processes from the seafloor to the air-sea interface." The Cabled Array, which straddles the Juan de Fuca and North American plates, is one of OOI's seven arrays worldwide (OOI, posting date uncertain1). Within the Cabled Array, there are seven primary nodes (PN) that are connected to a shore station in Pacific City, Oregon, through ~ 900 km of modified telecommunications cable (OOI, posting data uncertain2). This cable provides the PNs with high power and bandwidth that allows for near real-time interactive and adaptive investigation (OOI, posting date uncertain1). Each PN then delivers power and communication to a range of scientific instructions connected to it, such as those connected to the Axial Seamount PN3B (figure 10).

Figure (see Caption) Figure 10. Bathymetry map highlighting the various instruments connected to the Axial Seamount Primary Node (PN) 3B. PN3B is one of the seven PNs that comprise OOI's Cabled Array. The white cable (RSN Primary) that goes to the right of the image, connects PN3B and two other PNs (not shown) to the shore station in Pacific City, Oregon. For scale, there is a 250 m square on the map, located next to MJ03F. Image courtesy of Networked Observations and Visualization of the Axial Environment (NOVAE).

April 2015 eruption. Based on personal communication with Chadwick, around 0530 UTC on 24 April 2015 (2230 Pacific Time on 23 April), increased seismicity was recorded by the instruments in Axial's caldera.

This increased seismicity was the first indication of activity. On 24 April UTC, the daily earthquake count reached nearly 8,000 events/day (figure 11). Before the eruption, the daily earthquake count was generally less than 1,000 events/day (Delaney, 2015). From Wilcock (2015), Bulletin editors obtained a histogram of the daily earthquake count from 16 November 2014 to 14 June 2015; on the histogram, the daily earthquake count from 24 April UTC is represented by the largest bar (figure 11). Wilcock (2015) also provides animations of the preliminary locations of the earthquakes' epicenters at Axial from 23-24 April. The majority of the epicenters were largely clustered on the E side of the caldera, not far from the location of the 2011 eruption (Wilcock, 2015; Delaney, 2015).

Figure (see Caption) Figure 11. Preliminary earthquake histogram showing the daily earthquake counts at Axial Seamount from 16 November 2014 to 14 June 2015. On 24 April UTC, nearly 8,000 earthquakes were recorded (largest bar on the histogram). Dates on the histogram are in UTC. Taken from Wilcock (2015).

Around 0630 UTC on 24 April 2015 (2330 Pacific Time on 23 April), deformation at Axial Seamount increased considerably (Delaney, 2015). According to Delaney (2015), the instrument that measures bottom pressure and tilt on the seafloor at the Central Caldera site (figure 10) began to indicate deflation (subsidence). This deflationary event was reported to have lasted approximately 12 hours with the seafloor dropping as much as 2.4 m (Delaney, 2015; OSU, 2015). Bulletin editors learned from personal communication with Chadwick that the duration of subsidence at Axial may actually be on the order of ~10 days with the greatest amount of subsidence occurring within the first 24 hours of activity.

Although there was initial uncertainty regarding whether the observed deflation and earthquakes were associated with an eruption (or merely an intrusion), Chadwick and Nooner (2015) cited increases in seawater temperature data that occurred in the days and weeks following 24 April UTC. The observed increases suggested that lava erupted somewhere nearby on the seafloor (Chadwick and Nooner, 2015). The temperature data was collected by the three bottom pressure/tilt instruments, located in Central and Eastern Caldera and the International District Vent District (figure 10). The graph in figure 12 displays the increases documented in the temperature data (PMEL/EOI, 2015).

Figure (see Caption) Figure 12. Graph presenting seawater temperature data versus date (UTC, 1 April 2015 to 10 June 2015) collected by the bottom pressure and tilt instruments that are part of the OOI Cabled Array. These instruments detected increases in temperature that started on 24 April (indicated on graph) and peaked on 13 May 2015. By 10 June, the temperatures appear to have decreased to levels similar to before the eruption. The increases in temperature appear to be on the order of ~0.6-0.8 °C. Courtesy of PMEL/EOI, 2015

For reference, the 2.4 m deflation that occurred is similar to the amount detected in 2011 (BGVN 36:07). Delaney (2015) quoted Chadwick as saying that the amount of deflationary subsidence suggested that a similar amount of magma erupted in 2015 and during Axial's 2011 eruption.

References. Chadwick W and Nooner S, 2015, Successful forecast of the 24 April 2015 eruption at Axial Seamount, NOAA's Pacific Marine Environmental Laboratory's (PMEL) Earth-Ocean Interactions Program (EOI), URL: http://www.pmel.noaa.gov/eoi/axial_blog.html, accessed on 15 June 2015

Clague D A, Breyer B M, Paduan J B, Martin J F, Chadwick W W, Caress D W, Portner R A, Guilderson T P, McGann M L, Thomas H, Butterfield D A, Embley R W, 2013, Geologic history of the summit of Axial Seamount, Juan de Fuca Ridge. Geochem Geophys Geosystems, 14: 4403-4443

Delaney, J, 2015, Axial Activity Intensifies, URL: http://novae.ocean.washington.edu/file/Axial_Activity_Intensifies, accessed on 16 June 2015

NOVAE (Networked Observations and Visualization of the Axial Environment), 2015 http://novae.ocean.washington.edu/story/Latest_News, accessed on 15 June 2015

OSU (Oregon State University), 2015, Researchers think Axial Seamount off Northwest coast is erupting – right on schedule, URL: http://oregonstate.edu/ua/ncs/archives/2015/apr/researchers-think-axial-seamount-northwest-coast-erupting-–-right-schedule, accessed on 15 June 2015

OOI (Ocean Observatories Initiative), posting date uncertain1, OOI Frequently Asked Questions, URL: http://oceanobservatories.org/about/frequently-asked-questions/#01, accessed on 22 June 2015

OOI (Ocean Observatories Initiative), posting date uncertain2, Cabled Array, URL: http://oceanobservatories.org/infrastructure/regional-scale-nodes/, accessed on 17 June 2015

PMEL/EOI (NOAA's Pacific Marine Environmental Laboratory's Earth-Ocean Interactions Program), 2015, Data from the 24 April 2015 eruption at Axial Seamount, URL: http://www.pmel.noaa.gov/eoi/rsn/24April2015_event.html, accessed on 15-22 June 2015

Wilcock, W, 2015, Welcome to William Wilcock's desktop computer, URL: http://alben.ocean.washington.edu/, accessed on 16 June 2015.

Geologic Background. Axial Seamount rises 700 m above the mean level of the central Juan de Fuca Ridge crest about 480 km W of Cannon Beach, Oregon, to within about 1400 m of the sea surface. It is the most magmatically robust and seismically active site on the Juan de Fuca Ridge between the Blanco Fracture Zone and the Cobb offset. The summit is marked by an unusual rectangular-shaped caldera (3 x 8 km) that lies between two rift zones and is estimated to have formed about 31,000 years ago. The caldera is breached to the SE and is defined on three sides by boundary faults of up to 150 m relief. Hydrothermal vents with biological communities are located near the caldera fault and along the rift zones. Hydrothermal venting was discovered north of the caldera in 1983. Detailed mapping and sampling efforts have identified more than 50 lava flows emplaced since about 410 CE (Clague et al., 2013). Eruptions producing fissure-fed lava flows that buried previously installed seafloor instrumentation were detected seismically and geodetically in 1998 and 2011, and confirmed shortly after each eruption during submersible dives.

Information Contacts: William Chadwick, NOAA and Oregon State University, Hatfield Marine Science Center, 2115 S.E. Oregon State University Drive, Newport, OR 97365, USA; Scott Nooner, Department of Geography and Geology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403-5944, USA (URL: http://people.uncw.edu/nooners/Nooner/); Oregon State University, News and Research Communications, Corvalis, OR (URL: http://oregonstate.edu/ua/ncs/); William Wilcock, School of Oceanography, University of Washington, Marine Sciences Building, 1501 NE Boat Street, Seattle, WA 98195, USA (URL: http://faculty.washington.edu/wilcock/).


Ontakesan (Japan) — March 2015 Citation iconCite this Report

Ontakesan

Japan

35.893°N, 137.48°E; summit elev. 3067 m

All times are local (unless otherwise noted)


Eruptions: (a) March 2007 and (b) 27 September 2014 (~60 deaths and ~70 injured)

This Bulletin report on Ontakesan (Kiso-Ontakesan, Ontake) covers activity from November 2003 to November 2014. During this reporting interval, two eruptions occurred, both broadly described as phreatic, yet containing a minor component of identified juvenile magmatic material. The first eruption was on an unknown date in late March 2007, and the second eruption was on 27 September 2014. The 2014 eruption took place with a sudden onset and with few if any precursory warnings. The volcano is a famous tourist area to see color changes in autumn foliage, it also contains considerable alpine touristic infrastructure, including lodges. The 2014 eruption took place during the autumn color season on a Saturday. Hundreds of people were on the mountain at the time. The 2014 eruption included ashfall, pyroclastic flows, and related density currents. The eruption killed ~57 people and an additional 6 were still missing as of 27 October 2014 (Kyodo, 2014). The 2014 impulsive eruption was documented by an outstanding number of close-up photographs and videos taken by eyewitnesses.

Between the 2007 and 2014 eruptions, activity receded to background levels. Our last Bulletin report (BGVN 28:11) noted occasional white plumes during 2000 to 2003.

The data for this report was collected chiefly from online reports by the Japanese Meteorological Agency (JMA), the Geological Survey of Japan (GSJ), and the National Institute of Advanced Industrial Science and Technology (AIST).

Historically, activity at Ontakesan has consisted mainly of phreatic explosions every several hundred years. However, recent research cited in JMA (date unknown) indicates that over the past 10,000 years, four magmatic eruptions have also occurred. Although there are no reported records of historical eruptions before 1979, fumarolic activity was noted as ongoing for several hundred years near to Ontakesan's summit (Jigokudani and Hachotarumi). The period of activity after 1979 represents what appears to be Ontakesan's most active during the past 250 years (Oikawa, 2008).

2006–2007. The March 2007 eruption was preceded by minor inflation and an increase in seismic activity (JMA, date unknown). During mid- to late December 2006, instruments detected inflation of the volcanic edifice and an increase in shallow seismicity directly below the summit. During January 2007, instruments recorded 90 earthquakes on the 16th and 164 earthquakes on the 17th. On 25 January 2007, tremor occurred with the largest recorded amplitude in at least a year. Tremor had, according to a JMA plot, remained near zero during all of 2006. The January 2007 tremor was described as very low frequency, containing a 15- to 20-second-long component. Furthermore, GPS observations detected a small amount of crustal deformation preceding the seismic activity, indicating a slight inflation at Ontakesan.

On 16 March 2007, fumarolic activity increased; fumes at the summit were occasionally detected by a surveillance camera (at "Mitake Kurozawa," but the exact location was not found in English on maps in Ontakesan reports). Seismic and other data considered by JMA showed that an earthquake had occurred during late March, originating directly below Ontakesan. The specific dates of the seismicity and earthquake were not specified in the available reporting. Based on the data collected, JMA inferred that the earthquake had resulted from a magmatic intrusion that had advanced toward the surface reaching ~4 km below the volcano's summit.

A field study two months later, on 29 May 2007, noted fresh volcanic ash from Ontakesan's 79-7 crater. The ash reached ~200 m NE of the crater. This finding of fresh ash was believed to indicate that the 2007 eruption was not merely phreatic but involved some escape of juvenile components to the surface. The exact date of the eruption was undeterminable.

JMA cited a model by Nakamichi and others (2009) regarding the intrusion of a magmatic body and the subsequent 2007 eruption, to describe phreatic eruptions at Ontakesan (figure 12). The depths shown reflect but one set of depth values for the top of the intrusion ((a) in this case 3 km depth below the summit) and the zone of groundwater ((b) centered at ~2.4 km depth below the summit). Thus, figure 12 illustrates a basic model of the various processes involved in a phreatic eruption, which is defined by Harris (2000) as a ". . . steam eruption that produces no fresh magma. A common precursor of eruptive activity, it is caused when groundwater, heated by a magmatic source, flashes into steam."

Figure (see Caption) Figure 12. Diagrams (a and b) that JMA cited to help explain magma intrusion, steam generation, and related signals associated with a phreatic eruption. Courtesy of JMA, citing Nakamichi and others (2009).

Figure 12a considers an earlier pre-eruptive stage, where magma advanced upward to 3 km below the volcano's summit. Volcano-tectonic (VT) earthquakes resulted from breaking rock. Note that in the March 2007 eruption, the magma was thought to have advanced to 4 km depth below the summit and the tremor noted then was very-long period (VLP, because of the above-mentioned long-period (15-20 second) component).

Figure 12b considers a later stage of the intrusion event, where the magma ceased to advance towards the surface. The magma heated the groundwater, which expanded into steam. The pressure from the heated water and steam broke rock as it advanced towards the surface. Acoustical signals include VLP and long period (LP) earthquakes. In this model, the steam escaped through the ancestral vents, thus producing a phreatic eruption.

Eruption in September 2014. Available JMA and GSJ reports say very little about the period leading up to the September 2014 eruption. According to a news source (Asahi Shimbun, 2014b), during the early part of September, daily tremor peaked at 85 on 11 September and were followed by 3 to 27 tremor events per day starting on 12 September.

The JMA Executive Committee (2014) reported that on the morning of 27 September, a few hours before the eruption at 1152 Local Time (LT=UTC+9), there was no major unrest. They did record mild seismic events, tilt, and increased steaming; the noted data appearing from 1130 to 1210. The report noted that seismic signal recorded 11 minutes prior to the eruption was nearly flat, with only one small event, in contrast to the robust signal associated with the subsequent eruption. Tilt began 7 minutes prior to and peaked during the explosion.

GSJ (2014) stated: "A volcanic eruption occurred on September 27, 2014 at Mount Ontake on the border between Nagano and Gifu Prefectures. According to the Japan Meteorological Agency, the eruption began at about 11:52 JST [Japan Standard Time] (=UTC+9h) on September 27. It is estimated that the plume from this eruption reached a maximum height of 7000 m, and a pyroclastic flow cascaded down the mountain in a southwesterly direction for a distance of more than 3 km."

Additionally, about forty minutes later, the Tokyo Volcanic Ash Advisory Center (VAAC) noted that the plume resulting from the eruption ascended to 11 km above sea level (a.s.l.) extending to the E. The JMA raised the Alert Level to 3, and the level remained elevated throughout the reporting interval. Figure 13 provides an oblique view of the volcano with the approximate area of the eruption and the summit mountain lodge labelled.

Figure (see Caption) Figure 13. A DigitalGlobe Google image of Ontakesan with a label indicating the approximate area where the sudden eruption vented (on the S flank). For scale, the prominent crater atop this part of the cone is ~200 m in diameter. Several bodies were found within the mountain lodge and other infrastructure on and near the summit rim. Courtesy of BBC (2014b).

The 27 September eruption was captured by a camera system (Yamamoto, 2014; AIST, 2014b; GSJ, 2014) (figure 14). The term pyroclastic flow generally applies to laterally moving mixtures of hot gas and particles such as tephra and lithics; a broader term that includes ash cloud surges, etc. is pyroclastic density current (see Roche, 2015, and the references therein). In the case of the 2014 eruption, density currents occurred near the summit and on the western flank; some of the complexity may have been due to secondary explosions well downslope of the vent area (AIST, 2014b; Boyle and others, 2014). The density currents descended at variously reported maximum speeds of 30 to 72 km per hour (AIST, 2014b; Yamamoto, 2014). According to Boyle and others (2014), the pyroclastic density currents traveled more than 3 km down Ontakesan's S flank.

Figure (see Caption) Figure 14. Four photos of the Ontakesan 2014 eruption captured by the Chubu Regional Development Bureau's camera at Takigoshi on 27 September. [1] (1154 LT) The pyroclastic flow descended. [2] (1156 LT) A secondary plume rose. [3] (1201 LT) The plume released a downburst of ash. [4] (1205 LT) The plume developed laterally, spreading along the ground surface. Taken from Yamamoto (2014).

On 28 September, the day following the eruption, the GSJ conducted several aerial observations, utilizing media helicopters (GSJ, 2014). At 0800 LT, the height of the plume was ~500 m, heading S to SW. The scientists noted the eruption formed a new line of craters (figure 15) running NW to SE. These new craters resided 250–300 m to the SE of those formed during a previous eruption in 1979. The line of craters is roughly parallel to the 1979 line, but covers a wider area.

Figure (see Caption) Figure 15 Aerial view of Ontakesan from 28 September at 1636 LT. The Kengamine summit area, as depicted from the NW, released white plumes heading S to SE. The smaller plume in the foreground originated from a fissure crater on the W end of the new line of craters. The distant plume originated from the line of craters formed at Jigokudani, located SW of the summit . Additional photos of the eruption, similar to this one, are provided by the authors. Source: GSJ (2014).

GSJ also conducted expeditions to the Kaida Plateau, located ~6 km E to NE of the Kengamine summit, and collected ash samples on 28 September. A photo depicted in GSJ (2014) shows a light coating (on the order of several millimeters) of gray ash covering the leaves and horizontal surfaces of plants in the region. The geologists described the ash as "medium-to-fine-grain sand-sized particles" with a maximum diameter of 0.5 mm. Most of the ash was altered rock fragments and less than 10% was unaltered red-orange and crystalline fragments (as seen in figure 16). GSJ (2014) reported that, as a result of this ash analysis, the recent eruption was considered as phreatic (rather than predominantly magmatic).

Figure (see Caption) Figure 16. Samples collected at Ontakesan. (Top) A majority of this ash sample was altered. (Bottom) A sample with some fragments of unaltered ash. The AIST report also includes a detailed description of the methods used to gather/ analyze ash samples. Courtesy of AIST (2014a).

GSJ (2014) also noted that scientists had charted the main axis of ash fall from the 2014 eruption, based on the findings from their expeditions. The ash distribution extended towards Ontakesan's E to NE (red arrow, figure 17).

Figure (see Caption) Figure 17. Geological map of Ontakesan containing annotations relevant to the 2014 eruption. The main axis of ash distribution is noted by the red arrow. The line of craters formed by the 2014 eruption are marked approximately by a series of small red dots and a yellow line near the base of the red arrow. The 1979 line of craters is depicted as a row of green dots. The blue line denotes the known margin of the Younger Ontake Volcano formed ~100,000 years ago. Source: GSJ (2014).

News sources contributed the following. The ash resulting from the eruption was ~50 cm thick near the crater and up to 20 cm thick in lower areas (Adonai, 2014). Asahi Shimbun (2014b) also quoted a scholar, Takayuki Kaneko, as allegedly stating that the ash was "moist" and stuck together like "sesame seeds."

According to JMA, from 1 to 7 October, Ontakesan continued to emit ash, but the resultant plume height could not be determined due to poor visibility. On 7 October, the plume was observed to rise 300 m above the crater rim, drifting E. Tremor continued to be detected; the number of earthquakes detected from 27 September to 6 October are compiled in figure 18 (JMA daily reports).

Figure (see Caption) Figure 18. The number of earthquakes detected per day during 27 September to 6 October 2014. Data courtesy of JMA (daily reports); figure by Bulletin editors.

According to JMA, Ontakesan emitted ash plumes during 8–9 October, white plumes on 10 October, and plumes with only small amounts of ash during 10–14 October. During 8–14 October, tremors were below the detection limits. White plumes rose 100–200 m above the crater rim, drifting NE and SE, during 16–18 October. On 19 October, plumes rose to 600 m above crater.

Impact of eruption on people. As previously mentioned, according to news sources, the 27 September eruption killed 57 hikers on Ontakesan's slopes, and as of 27 October another 6 were missing (Kyodo, 2014). Furthermore, more than 70 were injured (RT, 2014). According to the Associated Press in Tokyo (2014), the explosion was the deadliest volcanic eruption in Japan in the post-WWII period.

According to the BBC (2014a), nearly 300 people were hiking on Ontakesan on the day of the eruption. The news article characterized the accounts of the eruption as consisting of falling ash and boulders, at times with sufficient density to cause several minutes of total darkness. Kuroda Terutoshi (Kuroda Terutoshi, 2014), posted a video of the eruption to YouTube that he took while hiking. The expanding ash plume engulfed a cabin on the slopes above him, and he was soon surrounded by the plume, which included dark ballistics and ashfall. The ash plume grew rapidly and continued downhill, as depicted in two other videos (Asahi Shimbun, 2014a and BBC News, 2014).

Boston Globe (2014) stated that rescue and recovery missions began on 28 September deploying more than 500 Japanese military and police. Metal and landmine detectors played a role in locating victims buried under ash (Asahi Shimbun, 2014c). National Geographic (2014) and Ogrodnik (2014) provide several photos of the rescue missions, derived from various news sources. According to Malm (2014), several of the casualties found during rescue operations were "still holding their smartphones." Lies and Meyers (2014) noted the halting of some initial search and recovery efforts on 30 September owing to increased tremor the night before raising concerns then about the return of volcanic activity.

On 6 October, Typhoon Phanfone (No. 18) came near to the Ngano Prefecture where Ontakesan is located (Asahi Shimbun, 2014b, c). Accompanied by heavy rains, a mixture of volcanic ash and rain formed into mud, making it hard for large helicopters to land near the summit. Rescue missions were halted on 15 October due to the wintery conditions despite people still missing. The article said that the search for bodies was expected to resume in the springtime.

References. T (?Pfeiffer, T), 2014, Ontake-san volcano (Japan): death toll from yesterday's eruption rises to more than 30, 28 September 2014, Volcano Discovery (URL: http://www.volcanodiscovery.com/on-take/news/48168/Ontake-san-volcano-Japan-death-toll-from-yesterday-s-eruption-rises-to-more-than-30.html) [accessed in June 2015]

AIST, 2014a, Analysis of Volcanic Ash Falling from the September 2014 Eruption of the Ontake Volcano, 28 September 2014, National Institute of Advanced Industrial Science and Technology (URL: https://www.gsj.jp/hazards/volcano/kazan-bukai/yochiren/ontake_ash_140928E.pdf)

AIST, 2014b, The Pyroclastic Flow Generated by the September 27, 2014 Eruption of the Ontake Volcano, 29 September 2014, National Institute of Advanced Industrial Science and Technology (URL: https://www.gsj.jp/hazards/volcano/kazan-bukai/yochiren/ontake_flow_140928E.pdf)

Asahi Shimbun, 2014a, Ontakesan eruption prediction was difficult, the Japan Meteorological Agency did not find any omens, 27 September 2014 (URL: http://www.asahi.com/articles/ASG9W5KFJG9WULBJ00D.html) [accessed in June 2015]

Asahi Shimbun, 2014b, Volcanologists: with few telltale signs, Mt. Ontakesan's eruption hard to predict, 28 September 2014, (URL: http://ajw.asahi.com/article/behind_news/social_affairs/AJ201409280022) [accessed in June 2015]

Asahi Shimbun, 2014c, Update: More victims of Mt. Ontakesan eruption found as typhoon nears, 4 October 2014 (URL: http://ajw.asahi.com/article/behind_news/social_affairs/AJ201410040056)

Associated Press in Tokyo, 2014, Hikers killed by Japanese volcano left poignant pictures of final moments, 5 October 2014, The Guardian (URL: http://www.theguardian.com/world/2014/oct/05/-sp-hikers-killed-japanese-volcano-pictures-final-moments) [accessed in June 2015]

Australian Associated Press with Australia Geographic staff, 2014, Japan Volcano Ontake an Extremely Rare Eruption, 29 September 2014, Australia Geographic (URL: www.australiangeographic.com.au/news/2014/09/japan-volcano-ontake-an-extremely-rare-eruption) [accessed in June 2015]

BBC News, 2014, Video: Japan volcano shoots rock & ash on Mount Ontake - BBC News, 29 September 2014, YouTube (URL: https://www.youtube.com/watch?v=aQtkoLxqUNQ) [accessed in June 2015]

BBC, 2014a, Japan's Mount Ontake volcanic eruption injures 30, 27 September 2014, British Broadcasting Corporation (URL: http://www.bbc.com/news/world-asia-29392810) [accessed in June 2015]

BBC, 2014b, Japan Mount Ontake Volcano: Death Toll Reaches 47, 1 October 2014, British Broadcasting Corporation (URL: www.bbc.com/news/world-asia-29440982) [accessed in June 2015]

Boston Globe, 2014, Military Helicopters Rescue People Stranded After Mt Ontake Eruption, 28 September 2014, Boston.com (URL: http://www.boston.com/news/world/asia/2014/09/28/military-helicopters-rescue-people-stranded-after-ontake-eruption/iW6wHPhW5K0rAsYM0EUe7H/video.html) [accessed in June 2015]

Boyle, D., Charlton, C., 2014, 36 Now Feared Dead in Japanese Volcano Disaster, 28 September 2014, Daily Mail (URL: http://www.dailymail.co.uk/news/article-2772458/More-30-hikers-dead-near-Japanese-volcano-erupted-without-warning-spewinf-eight-inch-blanket-ash.html) [accessed in June 2015]

GSJ, 2014, Ontake Volcano Information, 7 October 2014, Geological Survey of Japan (URL: https://www.gsj.jp/en/hazards/ontake2014/index.html) [accessed in June 2015]

Harris, 2002, Archaeology and volcanism, in The encyclopedia of volcanoes. Sigurdsson, H., Houghton, B., McNutt, S., Rymer, H., and Stix, J. (Eds.). pp. 1301-1314. Elsevier.

JMA, date unknown, 53. Ontakesan, Japan Meteorological Agency (JMA) (URL: http://www.data.jma.go.jp/svd/vois/data/tokyo/STOCK/souran_eng/volcanoes/053_ontakesan.pdf) [accessed in June 2015]

JMA Executive Committee, 2014, Prediction of Volcanic Eruptions Coordinating Committee Expanded Executive Committee, 21 pages, 28 September 2014, Japan Meteorological Agency (JMA) (URL: www.data.jma.go.jp/svd/vois/data/tokyo/STOCK/kaisetsu/CCPVE/shiryo/kakudai140928/kakudai140928_no01.pdf)

Kuroda Terutoshi, 2014, Ontake Eruption, original, 26 September 2014, YouTube (URL: https://www.youtube.com/watch?t=77&v=7Ea3uED1Zgc) [accessed in June 2015]

Kyodo, 2014, Ontake victims mourned a month after eruption as tourism industry scrambles to recover, 27 October 2014, Japan Times (URL: http://www.japantimes.co.jp/news/2014/10/27/national/ontake-victims-mourned-month-eruption-tourism-industry-scrambles-recover/) [accessed in June 2015]

Lies, E. and Meyers, C., 2014, Recovery of Japan Volcano Victims Suspended Amid Signs of Rising Activity, 30 September 2014, Reuters (URL: www.reuters.com/article/2014/09/30/us-japan-volcano-idUSKCN0HP07G20140930) [accessed in June 2015]

Nakamichi, H., Kumagai, H., Nakano, M., Okubo, M., Kimata, F., Ito, Y., Obara, K., 2014, Source mechanism of a very-long-period event at Mt Ontake, central Japan: Response of a hydrothermal system to magma intrusion beneath the summit, 10 November 2009, Journal of Volcanology and Geothermal Research (URL: http://www.sciencedirect.com/science/article/pii/S0377027309003588)

Malm, S., 2014, One last picture... that cost their lives: More than half the victims killed by erupting volcano in Japan were found clutching smartphones, 12 November 2014, Daily Mail (URL: http://www.dailymail.co.uk/news/article-2831305/One-selfie-cost-lives-half-victims-killed-erupting-volcano-Japan-clutching-smartphones-photos-lava-coming-them.html) [accessed in June 2015]

National Geographic, 2014, Pictures: Japanese Volcano that Killed Hikers, 29 September 2014 (URL: http://news.nationalgeographic.com/news/2014/09/pictures/140929-japan-volcano-ontake-pictures/) [accessed in June 2015]

Ogrodnik, I., 2014, IN PHOTOS: Powerful images as Japanese Volcano Mount Ontake Erupts, 1 October 2014, Global News (URL: http://globalnews.ca/news/1587737/in-photos-powerful-images-as-japans-mount-ontake-erupts/) [accessed in June 2015]

Oikawa, T., 2008, Re-examination of historical records and fumarolic activity of eruption records of the Ontake volcano, Japanese with English abstract, Geological Survey of Japan (GSJ) (URL: https://www.gsj.jp/data/bulletin/59_05_01.pdf)

Roche, O., 2015, Nature and Velocity of Pyroclastic Density Currents Inferred from Models of Entertainment of Substrate Lithic Clasts, Earth and Planetary Science Letters, 418, 115-125 (URL: http://adsabs.harvard.edu/abs/2015E&PSL.418..115R)

RT, 2014, Volcano erupts in central Japan, dozens injured (VIDEO, PHOTOS), 27 September 2014 (URL: http://rt.com/news/191124-japan-volcano-erupts-injured/) [access in June 2015]

Yamamoto, T., 2014, The Pyroclastic Density Currents Generated by the September 27, 2014 Phreatic Eruption of Ontake Volcano, Bulletin of the Geological Survey of Japan, number 65 (URL: https://www.gsj.jp/data/bulletin/65_09_03.pdf)

Geologic Background. The massive Ontakesan stratovolcano, the second highest volcano in Japan, lies at the southern end of the Northern Japan Alps. Ascending this volcano is one of the major objects of religious pilgrimage in central Japan. It is constructed within a largely buried 4 x 5 km caldera and occupies the southern end of the Norikura volcanic zone, which extends northward to Yakedake volcano. The older volcanic complex consisted of at least four major stratovolcanoes constructed from about 680,000 to about 420,000 years ago, after which Ontakesan was inactive for more than 300,000 years. The broad, elongated summit of the younger edifice is cut by a series of small explosion craters along a NNE-trending line. Several phreatic eruptions post-date the roughly 7300-year-old Akahoya tephra from Kikai caldera. The first historical eruption took place in 1979 from fissures near the summit. A non-eruptive landslide in 1984 produced a debris avalanche and lahar that swept down valleys south and east of the volcano. Very minor phreatic activity caused a dusting of ash near the summit in 1991 and 2007. A significant phreatic explosion in September 2014, when a large number of hikers were at or near the summit, resulted in many fatalities.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/)


Tungurahua (Ecuador) — March 2015 Citation iconCite this Report

Tungurahua

Ecuador

1.467°S, 78.442°W; summit elev. 5023 m

All times are local (unless otherwise noted)


Three periods of intense volcanism during late 2010-2011

Introduction. This Bulletin report covers activity at Tungurahua from November 2010 through December 2011, during which Ecuador's Instituto Geofísico-Escuela Politécnica Nacional (IG) reported three Eruptive Episodes (EE). The last Bulletin (BGVN 38:03) reported explosions and earthquakes at Tungurahua through late July 2010, followed by a lull in activity until October 2010.

This reporting period was characterized by ashfall; lahars; emissions of ash, water vapor, and gases such as SO2; strombolian activity; explosions; various types of earthquakes; and pyroclastic flows (PFs) among other events. Temporally, the majority of these events occurred during EE7 (November-December 2010), EE8 (April-May 2011), and EE9 (November-December 2011). Spatially, the processes such as lahars and PFs followed drainages, the geography of which is partly aided by maps and information in the next section. Intervening periods of low activity occurred during January-March 2011 and June-October 2011. The data presented here was gathered from various types of reports, special bulletins, and announcements published by IG.

Setting. Figure 54 displays a map of Tungurahua that includes ravines on its flanks and nearby inhabited areas. For ravines not seen in figure 54, such as those on the E flank, see figure 22 in BGVN 29:01. Table 8 in BGVN 29:01 gives the distances and direction of towns around Tungurahua, some of which are mentioned in this report. Mapa de Peligros–Tungurahua (Map of Hazards–Tungurahua) can also be viewed on IG's website, for a more general view of Tungurahua and environs.

Figure (see Caption) Figure 54. Map showing ravines and several inhabited areas around Tungurahua. Part of the network of stations that monitors seismic-acoustic activity is also shown. Deposits (noted in the key) were laid down in the August 2006 eruption. The Chambo and Patate Rivers join to form the Pastaza River, which flows E. Taken from Kelfoun and others (2009).

Eruptive episodes (EEs). In 2006, IG partnered with Japan's International Cooperation Agency to improve the monitoring of Tungurahua's seismic-acoustic activity, through the deployment of a network of broadband seismic sensors and infrared sensors. By 2008, the network had five stations (BMAS, BPAT, BRUN, BBIL and BULB), each located 5-7 km from Tungurahua's crater (figure 55). The sensors record seismic and acoustic signals propagated by volcanic explosions, emission tremors, booms, and chugging-type events. Information from the sensors and other observations, are used to define each EE. Table 18 shows the nine EEs registered from 2006-2011 based on information from IG's 2011 annual report on Tungurahua's explosive activity.

Figure (see Caption) Figure 55. Map of the network of stations that monitor seismic-acoustic activity at Tungurahua. Each station is equipped with broadband seismic sensors and infrared sensors. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).

Table 18. The nine Explosive Episodes (EEs) recorded by IG at Tungurahua since 2006. The table also shows the number of explosions recorded during each EE. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).

Eruptive Episode (EE) Eruptive Episode Number Number of explosions
14 July 2006-16 August 2006 EE1 118
25 February 2007-18 April 2007 EE2 366
13 July 2007-10 February 2008 EE3 1165
26 March 2008-27 June 2009 EE4 822
5 January 2010-19 March 2010 EE5 502
26 May 2010-28 July 2010 EE6 1331
22 November 2010-25 December 2010 EE7 110
22 April 2011-26 May 2011 EE8 64
27 November 2011-22 December 2011 EE9 55

Activity through mid-November 2010. After a four-month lull in activity, Tungurahua revived in November 2010, displaying somewhat elevated seismicity that included a series of volcano-tectonic (VT) earthquakes and a few low-energy explosions. IG's weekly report no.46, detailing activity from 15-21 November, stated that activity remained low with 88 long period (LP) earthquakes; 4 VT earthquakes; weak fumarolic activity; and weak emissions of water vapor and volcanic gases. Rains of varying intensities produced lahars from 15-19 November. On 16 November, the largest lahars of the week descended all of Tungurahua's ravines, with the most significant lahars descending the Mapayacu, Bilbao, and Vazcún ravines (figure 54).

EE7: 22 November-25 December 2010. A sudden increase in activity on 22 November, characterized by explosions in the afternoon and at night, marked the beginning of Tungurahua's EE7, according to IG's 2010 annual report on explosive activity. At 1408, a low-energy explosion was heard around Tungurahua and at the Observatorio del Volcán Tungurahua (OVT), located 14 km to the NW in Guadalupe. Movements of blocks along the upper flanks and an emission of low-to-moderate ash content that moved S accompanied the explosion. At 2235, a sudden large explosion generated an ash plume that rose to more than 7 km in altitude. This explosion triggered the ballistic expulsion of incandescent blocks, which descended ~1.5 km below the crater. Reports of ashfall and falls of gravel were received from communities to the W of Tungurahua, such as Choglontus.

Later, smaller explosions that produced emission columns 2-3 km above the crater were reported. Rains during the late afternoon generated a lahar that descended the Mapayacu ravine and temporarily dammed the Puela River. The Washington Volcanic Ash Advisory Center (VAAC) reported a 7.6 km altitude ash plume, during the night of 22 November, and ash emissions that rose 6.4 km in altitude on the morning of 23 November. EE7 continued until 25 December 2010. Figure 56 shows the number of explosions per day registered during this episode.

Figure (see Caption) Figure 56. Histogram showing the number of explosions per day recorded seismically at Tungurahua from 22 November to 25 December 2010 during EE7. 110 explosions were recorded, with the highest number of explosions occurring on 9 December. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).

According to IG's special bulletin no. 20, starting on 24 November 2010, the continuous ash emissions indicated the process of an open system, characterized by the constant generation of emission columns with variable amounts of ash due to an open and unsealed magma ascent path. Ashfall was reported in Ulba, Baños, Juive, Runtún, Bilbao, and Choglontus (settlements located on the NE-SW flanks).

Tungurahua's elevated activity continued through 3 December 2010 with (a) ash emissions, some rising ~3-4 km above the crater; (b) ashfall affecting communities such as Bilbao, Choglontus, El Manzano, and Cahuají; (c) strombolian activity with fountains up to ~1 km above the crater; (d) booming noises of varying magnitude; and (e) the expulsion of incandescent blocks, which rolled as much as ~1 km below the crater. On 29 November, an increase in SO2 was registered by the satellite-based Ozone Monitoring Instrument (OMI). IG also noted an increased SO2 flux through their fixed gas-monitoring stations.

On 4 December 2010, there was a very rapid and sudden increase in Tungurahua's seismic activity after no explosion signals were registered on the preceding days (figure 56). From 0830, the rapid increase in activity was manifested by (a) a speedy rise in the registered internal vibration; (b) an increase in the intensity and duration of booms and explosions; (c) an increase in the volume of emissions with higher ash levels; and (d) blocks moving more than 1.5 km below the crater. Residents in cities on the skirts of the volcano reported feeling vibrations. Due to this sudden increase in activity, the Alert Level was raised to Red by the National Secretariat of Risk Management, and populations around Tungurahua were evacuated.

Around 0939 on 4 December, observers saw pyroclastic flows (PFs) on Tungurahua's W and N flanks. At 0946, several PFs descended the Vazcún ravine. By 1130, PFs were still descending ravines on the W side, such as Mandur, Choglontus, and La Rea. The last PF of the day, at 1404, descended through the Juive sector. All the PFs on 4 December, descended ~2 km from the crater; the largest descended the Vazcún, Juive, and Mandur ravines.

During the afternoon of 4 December, IG noted a reduction in the intensity of activity, although a plume with moderate-to-high ash content rose ~3 km above the crater. Throughout the day, incandescent blocks rolled ~2 km down the flanks. During the evening, the seismic and surface activity continued to decrease. The Alert Level was lowered from Red to Orange.

An IG announcement, released on 4 December 2010, noted that this sudden increase in activity was unexpected in an open system. Special bulletin no. 23, also from 4 December, stated that Tungurahua's increased activity and the generation of PFs were associated with a rapid increase in the volume of magma entering the lower ducts of the volcanic vent and upon finding an open system, the magma was able to quickly rise to the crater and overflow as PFs.

After 4 December 2010, Tungurahua's activity returned to moderate levels. On 5 and 6 December, ashfall occurred in communities to the NW, W and SW. On 7 December, special bulletin no. 24 described activity marked by a constant emission of gases and ash, rising 2-3 km above the crater, occasionally accompanied by incandescent blocks, ejected hundreds of meters above the crater, before falling onto Tungurahua's flanks and rolling 1-2 km. According to that bulletin, secondary transport of ash also affected communities to the W of Tungurahua; crops in that area were reportedly covered by ash, no more than 1 mm thick.

On 9 December 2010, the maximum number of explosions for this EE was recorded (figure 56), and a PF descended also the Cusúa ravine. Tungurahua's explosive activity decreased thereafter. Between 9 and 23 December, activity included: incandescent blocks ejected above the crater rolled down Tungurahua's flanks; plumes containing variable amounts of ash often rose as high as 2-3 km above the crater; ashfall was reported in nearby communities; explosions caused vibrations of windows, "cannon shots", and plumes; and lahars. According to special bulletin no. 26, from 13 December, there was an increase in the number of LP earthquakes and from15 December, several VT earthquakes were recorded.

Between 24 and 25 December 2010, IG registered a series of small-to-moderate-sized explosions. Figure 56 shows 10 explosions were recorded on 25 December, after which explosive activity was reported to have stopped. Special bulletin no. 1, from 5 January 2011, stated Tungurahua's monitoring system had detected: smaller plumes with lower ash content; no explosions since 25 December 2010; fewer LP earthquakes and emission tremors (26 December 2010, 36 LPs and 4 emission tremors were recorded, while on 2 January 2011, 18 LPs and 1 emission tremor); decreased SO2 emissions (26 December, 2,200 tons/day of SO2 were recorded, but days before 5 January, 200 tons/day were recorded); and less pressure in the upper part of the cone. IG also reported 10 small VT earthquakes, interpreted to represent the entrance of new magma into the volcanic system and precursors to an increase in explosive activity.

Lull during January-March 2011. Weekly reports in January described moderate activity until 5 January, after which activity was moderate to low through 18 January. Special bulletin no.2 stated that between 5 and 17 January emissions mainly consisted of water vapor. January ended with activity being low and it remained so for the next two months (figure 57).

Figure (see Caption) Figure 57. Histogram showing the number of explosions recorded per day at Tungurahua from January to December 2011. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).

EE8: 22 April-26 May 2011. Tungurahua's monitoring stations began to register an episode of volcanic tremor at 1714 on 20 April 2011. A plume with low-to-moderate ash content rose 3 km above the crater and drifted SW. This was the first major sign of surface activity since the beginning of 2011. An IG announcement from 20 April stated that small seismic fracture events were observed. Deformation observed in the NW quadrant since February 2011 had recently increased. During the night of 20 April, IG personnel witnessed strombolian activity, accompanied by constant booms of moderate intensity. Incandescent blocks also rolled 1 km down the flanks.

At 1512 on 22 April 2011, a moderate-sized explosion signaled the beginning of Tungurahua's EE8, according to the 2011 annual report on explosive activity. EE8 continued until 26 May and was characterized by a total of 64 explosions (figure 58). According to IG's weekly report no. 16, detailing activity from 18-24 April, low-intensity rains produced muddy water in some of Tungurahua's ravines. During this interval, plumes with moderate-to-high ash levels rose 5 km above the crater. On some nights, strombolian activity was observed, and ashfall of varying intensities affected numerous settlements including Choglontus, Bilbao (figure 59), El Manzano, Puela, Cusúa, Guadalupe, Baños, Ulba, and Cevallos. SO2 was measured at 571 tons/day on 19 April and increased each day until it reached a maximum of 6,015 tons/day on 24 April.

Figure (see Caption) Figure 58. Histogram showing the number of explosions recorded per day at Tungurahua from 22 April to 26 May 2011. In total, 64 explosions were recorded, with the maximum number of explosions occurring on 21 May. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).
Figure (see Caption) Figure 59. (A) Ash covering the surface of a solar panel in Bilbao (8 km W of Tungurahua) on 24 April 2011. (B) Ash covering vegetation in Bilbao on 24 April 2011. In Bilbao, ash accumulated over 12 hours due to constant emissions and reached a thickness of ~3 mm. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).

According to special bulletin no. 5 from 26 April 2011, during 20-26 April ash emissions were accompanied by booms of varying intensity, lava fountains, and incandescent blocks rolling down the upper flanks. Data collected by inclinometers showed continued deformation in the NW quadrant.

On 26 April 2011, volcanic activity increased (figure 58), starting around 1245, with ash emissions rising 8-12 km above the crater. Areas to the NW and W experienced ashfall. OVT received reports that activity caused vibrations of the ground in areas close to the volcano. In Baños (8 km N), vibrations of doors and windows were reported. The National Secretariat of Risk Management declared an Orange Alert Level for areas around the volcano and evacuated families in Cusúa, Bilbao, and Chacauco. A widening of the volcanic cone was also detected on 26 April.

Another increase in activity occurred on 29 April 2011 and lasted for 48 hours. At ~0100, an increase in seismic amplitude and the presence of harmonic tremor were registered. Emissions with moderate-to-high ash content were often observed rising 2-3 km above the crater, moving NE. Baños, Runtún, Ulba, Juive and Cusúa received notable ashfall, while in Guadalupe, ash was lightly deposited. Emissions also rose 7 km above the crater and drifted mainly SE toward uninhabited areas. Strombolian eruptions also ejected blocks from the crater.

According to special bulletin no. 7, published on 3 May, the intensity of Tungurahua's emissions started to slowly decrease on 1 May, until returning to levels similar to those observed at the beginning of this EE. Special bulletin no. 7 also stated that Tungurahua's seismic and deformation monitoring systems continued to show evidence of internal pressurization. That bulletin also mentioned that IG and the French Institute for Research and Development (IRD) had estimated that ~1.6x106 m3 to 3x106 m3 of ash was deposited in areas around Tungurahua during an unstated amount of time; the maximum thickness reached 15.5 mm (figure 60).

Figure (see Caption) Figure 60. Map of accumulated ash thickness in areas around Tungurahua as measured on 2 May 2011. The interval over which the ash accumulated was unstated. Thicknesses were measured in mm. The English translations for the Spanish words in the key are: Espesor, thickness; Cabecera Cantonal, cantonal capital; and Cantones, districts. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).

Special bulletin no. 8 from 6 May 2011 stated that since 3 May, surface activity had continued to decrease with respect to the height, frequency, and ash content of the plumes and in the number of explosions. Nevertheless, IG warned that the decrease in emissions did not signal the end of this EE. Evidence of increasing internal pressure, presumably caused by the ascent of a new volume of magma towards the upper volcanic ducts, continued to be registered through deformation recorded by GPS and inclinometers, rock fracture earthquakes, and constant emission of volcanic gases. SO2 fluxes surpassed 2,000 tons/day.

After 6 May, Tungurahua experienced a slight lull in its eruptive activity for ~ 10 days; however, roaring was sometimes still heard, ashfall was reported, and on 10 May an explosion produced an ash plume that rose 5 km above the crater. More consistent and elevated activity resumed at 2222 on 16 May when gas-and-ash plumes rose between 1.5 and 2 km above the crater and drifted NE. At dawn on 17 May, significant ashfall was reported in Río Negro, ~25 km E of Baños. Special bulletin no. 9 (issued 17 May) said that a slight decrease in deformation was recorded by inclinometers as well as a reduction in the gas fluxes (less than 300 tons/day were recorded through 16 May). On the afternoon of 17 May, new fumaroles were also identified ~ 1,000 m below the summit on the W flank.

Through 19 May 2011, Tungurahua continued emitting vapor and gas containing variable amounts of ash. Ashfall affected communities in the NE-E-SE sectors such as Río Negro, Baños, Runtún, Cusúa, and Bilbao. The greatest measured thickness was 3 mm in Trigal, located to the SE. At midday on 19 May, observers witnessed explosions of significant sizes producing ash plumes that rose 3 km above the crater and drifted W and SW.

During 18-25 May 2011, seismic activity was characterized by 37 explosions, the majority of which occurred on 21 May (figure 58). Some of the explosions generated "cannon shots" that vibrated structures in nearby areas. Activity was characterized by high seismicity, including LP events and tremors. On 25 May, surface activity had decreased, but seismicity was moderate-to-high, deformation continued, and SO2 was being still emitted.

Constant rains during 27-28 May generated lahars and the swelling of rivers. On 27 May, a large lahar descended the Pingullo ravine, halting traffic along the road between Baños and Penipe. Muddy water moved down the Juive, Vazcún, Pondoa, Bilbao, Mapayacu, Ulba, and Achupashal ravines. On 28 May, flows of muddy water traveled down the Bilbao, Pondoa, Juive, and La Pirámide ravines; swelling of the Chambo and Puela rivers was reported; and the Ulba River doubled its volume and carried large blocks of rock. At the end of May 2011, activity returned to moderate levels.

Lull from June to October 2011. A second lull in explosive activity occurred (figure 57). On 29 July, 20 landslides took place along the Baños access road, a vital escape route.

On 7 October 2011, the Washington VAAC reported an ash plume that rose ~1 km above Tungurahua's crater and drifted W. On 24 October, another ash plume rose slightly over 2 km above the crater and drifted W. However, IG stated they had not observed any ash emissions since June. On 9 November, the Washington VAAC reported an ash plume, while IG reported only gas-and-steam emissions. On 15 October, IG also reported the reactivation of a fumarole, first observed in May 2011, on Tungurahua's W flank. The fumarole's activity lessened during the following week.

EE9: 27 November-22 December 2011. Three explosions (figure 61) on 27 November marked the beginning of Tungurahua's EE9, which continued to 22 December.

Figure (see Caption) Figure 61. Histogram showing the number of explosions recorded per day at Tungurahua from 27 November to 22 December 2011. During this EE, 55 explosions were recorded and the maximum number of explosions was registered on 4 and 5 December. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG).

On 27 November 2011, seismic activity began steadily increasing at 1540. At 1700, explosions of varying sizes were detected. Booms and "cannon shots" produced by the explosions were heard in areas close to Tungurahua. As activity progressed, explosions generated PFs that descended ravines on the NW and W flanks. The explosions also ejected incandescent blocks that rolled to ~1 km below the crater. Four VT earthquakes were also registered beginning at 1650. IG received reports of ashfall in El Manzano and Bilbao; deposits of coarse-grained ash in Pillate; ash with shards in Cotaló; and only shards in Cusúa. Later, PFs descended the S and SW flanks. Distances traveled by the PFs on the NW, W, S and SW flanks were unstated.

During the last days of November 2011, activity remained high. On 28 November, an explosion ejected incandescent material and generated a PF in the Achupashal ravine. There were also almost constant booms of moderate-to-high intensity, lava fountains, and ejected incandescent blocks that traveled ~1 km down the W and NW flanks. A constant ash plume rose 3 km over the summit. Small PFs descended the S flank, and ash fell in El Manzano, Choglontus, and Runtún. At night, incandescent blocks were observed being ejected above the crater before they descended 400-500 m down the flanks.

On 29 November, two PFs were observed: the first traveled ~500 m down the NW flank; the second traveled ~1 km down the Pingullo ravine. Almost-constant booms of moderate-to-high intensity and muddy water flowing down several ravines on the W side were noted. Ash-and-gas plumes rose up to 4 km above the crater, and tremor was constant. On 30 November, plumes rose to average heights of 2 km and minor ashfall in Baños and Río Verde was reported.

Activity remained high during the beginning of December. On the night of 1 December, a decrease in tremor amplitude coincided with an increase in the number of explosions. Strong "cannon shots" were generated by some of the explosions and incandescent blocks ejected onto the flanks rolling 1 km downslope. Heavy rains during the night led to the descent of lahars in the Mapayacu and La Pampa ravines and the swelling of the Vazcún River. Early on 2 December, an increase in tremor amplitude corresponded with moderate to strong booms. An ash plume later rose 1.5 km above the crater, drifting E.

During the night of 2 December and dawn of 3 December, IG noted two periods with increased tremor amplitude, during which a great volume of incandescent blocks was expelled and high intensity booms resonated through nearby communities. On 3 December, several PFs traveled ~1.5 km in the upper parts of La Rea and Ingapirca ravines and ravines on the NW flank. A plume with high ash content rose 2-3 km above the crater. Ash fell in settlements, including Bilbao, Cusúa, El Manzano, and Penipe.

During 4-5 December, the maximum number of explosions for EE9 was recorded (figure 61). On both days, seismicity consisted of constant tremor intermixed with explosions. On 4 December, strong booms and "cannon shots", both associated with explosive activity, were reported by communities close to Tungurahua. A plume with moderate-to-high ash content rose 4 km high, a small PF was noted, and ash fell in Bilbao, Cusúa, and El Manzano. On 5 December, an ash plume rose 1 km above the crater and drifted N and NE, leading to ashfall in Baños and Runtún. Booms of low to moderate intensity were also reported. On 7 December, explosions generated "cannon shots" of moderate intensity; blocks descended the flanks generating noises; a plume with moderate ash content rose 1.5 km above the crater and drifted W; and Cusúa and Chacauco received ashfall. On 8 December, similar conditions prevailed, but some plumes also rose as high as 4 km above the crater.

Activity declined on 9 December according to special bulletin no. 18. Emissions contained only water vapor. SO2 fluxes had fallen to 500 tons/day, which was significantly less than the maximum 8,000 tons/day measured after 28 November. Special bulletin no. 18 noted that despite these declines, seismic events such as LP and VT earthquakes were still recorded (between 60 and 170 LP earthquakes were registered daily). That special bulletin also remarked that the network for deformation monitoring did not register any evidence of the ascent of a new volume of magma towards the surface. This decline in activity lasted until 21 December.

From about 0830 on 22 December, several seismic events indicated the movement of fluids within Tungurahua's interior. Three explosions produced ash plumes that rose less than 500 m above the crater, the second explosion of which led to a PF that descended 300-400 m down the NW flank. That afternoon, a high-energy explosion generated two PFs that descended the Achupashal and La Hacienda ravines. An ash plume rose 4 km above the crater and drifted NW. The PFs descended to a maximum of 2 km below the crater, without reaching inhabited or cultivated areas. Ashfall was reported in N and W communities. Ash-and-gas plumes continued, and at night strombolian activity ejected blocks ~500 m above the crater, which landed and rolled 500 m below the crater.

For the rest of December 2011, activity was considered moderate. After 22 December, ash was often deposited in areas to the SW of Tungurahua such as El Manzano and Choglontus, where up to 2-4 mm of ash was deposited. On 23 December constant gas-and-ash emissions rose ~200 m above the crater and were carried SW. Ashfall was reported in El Manzano, Choglontus and Chacauco. On 24 December, no surface observations were made, but there were reports of ashfall in El Manzano, Choglontus and Cahuají. On 25 December, an emission with moderate-to-high ash content was observed rising 500 m above the crater and drifted W. Ashfall was reported in El Manzano. From 27 to 29 December, the area around Tungurahua was cloudy and no reports of booms or ashfall were received. On the last day of 2011, small emissions of water vapor and minor rains were reported.

References. Kelfoun, K., Samaniego, P., Palacios, P., Barba, D., 2009. Testing the suitability of frictional behaviour for pyroclastic flow simulation by comparison with a well-constrained eruption at Tungurahua volcano (Ecuador). Bulletin of Volcanology, v. 71(9), p. 1057-1075 (URL: http://dx.doi.org/10.1007/s00445-009-0286-6)

Geologic Background. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Apartado 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).

Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

Atmospheric Effects (1980-1989)  Atmospheric Effects (1995-2001)

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subregion and subject.

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

08/1997 (BGVN 22:08) False Report of Mount Pinokis Eruption

False report of volcanism intended to exclude would-be gold miners

12/1997 (BGVN 22:12) False Report of Somalia Eruption

Press reports of Somalia's first historical eruption were likely in error

11/1999 (BGVN 24:11) False Report of Sea of Marmara Eruption

UFO adherent claims new volcano in Sea of Marmara

05/2003 (BGVN 28:05) Har-Togoo

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

False report of activity; confusion caused by burning dung in a lava tube



False Report of Mount Pinokis Eruption (Philippines) — August 1997

False Report of Mount Pinokis Eruption

Philippines

7.975°N, 123.23°E; summit elev. 1510 m

All times are local (unless otherwise noted)


False report of volcanism intended to exclude would-be gold miners

In discussing the week ending on 12 September, "Earthweek" (Newman, 1997) incorrectly claimed that a volcano named "Mount Pinukis" had erupted. Widely read in the US, the dramatic Earthweek report described terrified farmers and a black mushroom cloud that resembled a nuclear explosion. The mountain's location was given as "200 km E of Zamboanga City," a spot well into the sea. The purported eruption had received mention in a Manila Bulletin newspaper report nine days earlier, on 4 September. Their comparatively understated report said that a local police director had disclosed that residents had seen a dormant volcano showing signs of activity.

In response to these news reports Emmanuel Ramos of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) sent a reply on 17 September. PHIVOLCS staff had initially heard that there were some 12 alleged families who fled the mountain and sought shelter in the lowlands. A PHIVOLCS investigation team later found that the reported "families" were actually individuals seeking respite from some politically motivated harassment. The story seems to have stemmed from a local gold rush and an influential politician who wanted to use volcanism as a ploy to exclude residents. PHIVOLCS concluded that no volcanic activity had occurred. They also added that this finding disappointed local politicians but was much welcomed by the residents.

PHIVOLCS spelled the mountain's name as "Pinokis" and from their report it seems that it might be an inactive volcano. There is no known Holocene volcano with a similar name (Simkin and Siebert, 1994). No similar names (Pinokis, Pinukis, Pinakis, etc.) were found listed in the National Imagery and Mapping Agency GEOnet Names Server (http://geonames.nga.mil/gns/html/index.html), a searchable database of 3.3 million non-US geographic-feature names.

The Manila Bulletin report suggested that Pinokis resides on the Zamboanga Peninsula. The Peninsula lies on Mindanao Island's extreme W side where it bounds the Moro Gulf, an arm of the Celebes Sea. The mountainous Peninsula trends NNE-SSW and contains peaks with summit elevations near 1,300 m. Zamboanga City sits at the extreme end of the Peninsula and operates both a major seaport and an international airport.

[Later investigation found that Mt. Pinokis is located in the Lison Valley on the Zamboanga Peninsula, about 170 km NE of Zamboanga City and 30 km NW of Pagadian City. It is adjacent to the two peaks of the Susong Dalaga (Maiden's Breast) and near Mt. Sugarloaf.]

References. Newman, S., 1997, Earthweek, a diary of the planet (week ending 12 September): syndicated newspaper column (URL: http://www.earthweek.com/).

Manila Bulletin, 4 Sept. 1997, Dante's Peak (URL: http://www.mb.com.ph/).

Simkin, T., and Siebert, L., 1994, Volcanoes of the world, 2nd edition: Geoscience Press in association with the Smithsonian Institution Global Volcanism Program, Tucson AZ, 368 p.

Information Contacts: Emmanuel G. Ramos, Deputy Director, Philippine Institute of Volcanology and Seismology, Department of Science and Technology, PHIVOLCS Building, C. P. Garcia Ave., University of the Philippines, Diliman campus, Quezon City, Philippines.


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


Press reports of Somalia's first historical eruption were likely in error

Xinhua News Agency filed a news report on 27 February under the headline "Volcano erupts in Somalia" but the veracity of the story now appears doubtful. The report disclosed the volcano's location as on the W side of the Gedo region, an area along the Ethiopian border just NE of Kenya. The report had relied on the commissioner of the town of Bohol Garas (a settlement described as 40 km NE of the main Al-Itihad headquarters of Luq town) and some or all of the information was relayed by journalists through VHF radio. The report claimed the disaster "wounded six herdsmen" and "claimed the lives of 290 goats grazing near the mountain when the incident took place." Further descriptions included such statements as "the volcano which erupted two days ago [25 February] has melted down the rocks and sand and spread . . . ."

Giday WoldeGabriel returned from three weeks of geological fieldwork in SW Ethiopia, near the Kenyan border, on 25 August. During his time there he inquired of many people, including geologists, if they had heard of a Somalian eruption in the Gedo area; no one had heard of the event. WoldeGabriel stated that he felt the news report could have described an old mine or bomb exploding. Heavy fighting took place in the Gedo region during the Ethio-Somalian war of 1977. Somalia lacks an embassy in Washington DC; when asked during late August, Ayalaw Yiman, an Ethiopian embassy staff member in Washington DC also lacked any knowledge of a Somalian eruption.

A Somalian eruption would be significant since the closest known Holocene volcanoes occur in the central Ethiopian segment of the East African rift system S of Addis Ababa, ~500 km NW of the Gedo area. These Ethiopian rift volcanoes include volcanic fields, shield volcanoes, cinder cones, and stratovolcanoes.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Giday WoldeGabriel, EES-1/MS D462, Geology-Geochemistry Group, Los Alamos National Laboratory, Los Alamos, NM 87545; Ayalaw Yiman, Ethiopian Embassy, 2134 Kalorama Rd. NW, Washington DC 20008.


False Report of Sea of Marmara Eruption (Turkey) — November 1999

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

Following the Ms 7.8 earthquake in Turkey on 17 August (BGVN 24:08) an Email message originating in Turkey was circulated, claiming that volcanic activity was observed coincident with the earthquake and suggesting a new (magmatic) volcano in the Sea of Marmara. For reasons outlined below, and in the absence of further evidence, editors of the Bulletin consider this a false report.

The report stated that fishermen near the village of Cinarcik, at the E end of the Sea of Marmara "saw the sea turned red with fireballs" shortly after the onset of the earthquake. They later found dead fish that appeared "fried." Their nets were "burned" while under water and contained samples of rocks alleged to look "magmatic."

No samples of the fish were preserved. A tectonic scientist in Istanbul speculated that hot water released by the earthquake from the many hot springs along the coast in that area may have killed some fish (although they would be boiled rather than fried).

The phenomenon called earthquake lights could explain the "fireballs" reportedly seen by the fishermen. Such effects have been reasonably established associated with large earthquakes, although their origin remains poorly understood. In addition to deformation-triggered piezoelectric effects, earthquake lights have sometimes been explained as due to the release of methane gas in areas of mass wasting (even under water). Omlin and others (1999), for example, found gas hydrate and methane releases associated with mud volcanoes in coastal submarine environments.

The astronomer and author Thomas Gold (Gold, 1998) has a website (Gold, 2000) where he presents a series of alleged quotes from witnesses of earthquakes. We include three such quotes here (along with Gold's dates, attributions, and other comments):

(A) Lima, 30 March 1828. "Water in the bay 'hissed as if hot iron was immersed in it,' bubbles and dead fish rose to the surface, and the anchor chain of HMS Volage was partially fused while lying in the mud on the bottom." (Attributed to Bagnold, 1829; the anchor chain is reported to be on display in the London Navy Museum.)

(B) Romania, 10 November 1940. ". . . a thick layer like a translucid gas above the surface of the soil . . . irregular gas fires . . . flames in rhythm with the movements of the soil . . . flashes like lightning from the floor to the summit of Mt Tampa . . . flames issuing from rocks, which crumbled, with flashes also issuing from non-wooded mountainsides." (Phrases used in eyewitness accounts collected by Demetrescu and Petrescu, 1941).

(C) Sungpan-Pingwu (China), 16, 22, and 23 August 1976. "From March of 1976, various large anomalies were observed over a broad region. . . . At the Wanchia commune of Chungching County, outbursts of natural gas from rock fissures ignited and were difficult to extinguish even by dumping dirt over the fissures. . . . Chu Chieh Cho, of the Provincial Seismological Bureau, related personally seeing a fireball 75 km from the epicenter on the night of 21 July while in the company of three professional seismologists."

Yalciner and others (1999) made a study of coastal areas along the Sea of Marmara after the Izmet earthquake. They found evidence for one or more tsunamis with maximum runups of 2.0-2.5 m. Preliminary modeling of the earthquake's response failed to reproduce the observed runups; the areas of maximum runup instead appeared to correspond most closely with several local mass-failure events. This observation together with the magnitude of the earthquake, and bottom soundings from marine geophysical teams, suggested mass wasting may have been fairly common on the floor of the Sea of Marmara.

Despite a wide range of poorly understood, dramatic processes associated with earthquakes (Izmet 1999 apparently included), there remains little evidence for volcanism around the time of the earthquake. The nearest Holocene volcano lies ~200 km SW of the report location. Neither Turkish geologists nor scientists from other countries in Turkey to study the 17 August earthquake reported any volcanism. The report said the fisherman found "magmatic" rocks; it is unlikely they would be familiar with this term.

The motivation and credibility of the report's originator, Erol Erkmen, are unknown. Certainly, the difficulty in translating from Turkish to English may have caused some problems in understanding. Erkmen is associated with a website devoted to reporting UFO activity in Turkey. Photographs of a "magmatic rock" sample were sent to the Bulletin, but they only showed dark rocks photographed devoid of a scale on a featureless background. The rocks shown did not appear to be vesicular or glassy. What was most significant to Bulletin editors was the report author's progressive reluctance to provide samples or encourage follow-up investigation with local scientists. Without the collaboration of trained scientists on the scene this report cannot be validated.

References. Omlin, A, Damm, E., Mienert, J., and Lukas, D., 1999, In-situ detection of methane releases adjacent to gas hydrate fields on the Norwegian margin: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Yalciner, A.C., Borrero, J., Kukano, U., Watts, P., Synolakis, C. E., and Imamura, F., 1999, Field survey of 1999 Izmit tsunami and modeling effort of new tsunami generation mechanism: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Gold, T., 1998, The deep hot biosphere: Springer Verlag, 256 p., ISBN: 0387985468.

Gold, T., 2000, Eye-witness accounts of several major earthquakes (URL: http://www.people.cornell.edu/ pages/tg21/eyewit.html).

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

48.831°N, 101.626°E; summit elev. 1675 m

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

In December 2002 information appeared in Mongolian and Russian newspapers and on national TV that a volcano in Central Mongolia, the Har-Togoo volcano, was producing white vapors and constant acoustic noise. Because of the potential hazard posed to two nearby settlements, mainly with regard to potential blocking of rivers, the Director of the Research Center of Astronomy and Geophysics of the Mongolian Academy of Sciences, Dr. Bekhtur, organized a scientific expedition to the volcano on 19-20 March 2003. The scientific team also included M. Ulziibat, seismologist from the same Research Center, M. Ganzorig, the Director of the Institute of Informatics, and A. Ivanov from the Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences.

Geological setting. The Miocene Har-Togoo shield volcano is situated on top of a vast volcanic plateau (figure 1). The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Pliocene and Quaternary volcanic rocks are also abundant in the vicinity of the Holocene volcanoes (Devyatkin and Smelov, 1979; Logatchev and others, 1982). Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Figure (see Caption) Figure 1. Photograph of the Har-Togoo volcano viewed from west, March 2003. Courtesy of Alexei Ivanov.

Observations during March 2003. The name of the volcano in the Mongolian language means "black-pot" and through questioning of the local inhabitants, it was learned that there is a local myth that a dragon lived in the volcano. The local inhabitants also mentioned that marmots, previously abundant in the area, began to migrate westwards five years ago; they are now practically absent from the area.

Acoustic noise and venting of colorless warm gas from a small hole near the summit were noticed in October 2002 by local residents. In December 2002, while snow lay on the ground, the hole was clearly visible to local visitors, and a second hole could be seen a few meters away; it is unclear whether or not white vapors were noticed on this occasion. During the inspection in March 2003 a third hole was seen. The second hole is located within a 3 x 3 m outcrop of cinder and pumice (figure 2) whereas the first and the third holes are located within massive basalts. When close to the holes, constant noise resembled a rapid river heard from afar. The second hole was covered with plastic sheeting fixed at the margins, but the plastic was blown off within 2-3 seconds. Gas from the second hole was sampled in a mechanically pumped glass sampler. Analysis by gas chromatography, performed a week later at the Institute of the Earth's Crust, showed that nitrogen and atmospheric air were the major constituents.

Figure (see Caption) Figure 2. Photograph of the second hole sampled at Har-Togoo, with hammer for scale, March 2003. Courtesy of Alexei Ivanov.

The temperature of the gas at the first, second, and third holes was +1.1, +1.4, and +2.7°C, respectively, while air temperature was -4.6 to -4.7°C (measured on 19 March 2003). Repeated measurements of the temperatures on the next day gave values of +1.1, +0.8, and -6.0°C at the first, second, and third holes, respectively. Air temperature was -9.4°C. To avoid bias due to direct heating from sunlight the measurements were performed under shadow. All measurements were done with Chechtemp2 digital thermometer with precision of ± 0.1°C and accuracy ± 0.3°C.

Inside the mouth of the first hole was 4-10-cm-thick ice with suspended gas bubbles (figure 5). The ice and snow were sampled in plastic bottles, melted, and tested for pH and Eh with digital meters. The pH-meter was calibrated by Horiba Ltd (Kyoto, Japan) standard solutions 4 and 7. Water from melted ice appeared to be slightly acidic (pH 6.52) in comparison to water of melted snow (pH 7.04). Both pH values were within neutral solution values. No prominent difference in Eh (108 and 117 for ice and snow, respectively) was revealed.

Two digital short-period three-component stations were installed on top of Har-Togoo, one 50 m from the degassing holes and one in a remote area on basement rocks, for monitoring during 19-20 March 2003. Every hour 1-3 microseismic events with magnitude <2 were recorded. All seismic events were virtually identical and resembled A-type volcano-tectonic earthquakes (figure 6). Arrival difference between S and P waves were around 0.06-0.3 seconds for the Har-Togoo station and 0.1-1.5 seconds for the remote station. Assuming that the Har-Togoo station was located in the epicentral zone, the events were located at ~1-3 km depth. Seismic episodes similar to volcanic tremors were also recorded (figure 3).

Figure (see Caption) Figure 3. Examples of an A-type volcano-tectonic earthquake and volcanic tremor episodes recorded at the Har-Togoo station on 19 March 2003. Courtesy of Alexei Ivanov.

Conclusions. The abnormal thermal and seismic activities could be the result of either hydrothermal or volcanic processes. This activity could have started in the fall of 2002 when they were directly observed for the first time, or possibly up to five years earlier when marmots started migrating from the area. Further studies are planned to investigate the cause of the fumarolic and seismic activities.

At the end of a second visit in early July, gas venting had stopped, but seismicity was continuing. In August there will be a workshop on Russian-Mongolian cooperation between Institutions of the Russian and Mongolian Academies of Sciences (held in Ulan-Bator, Mongolia), where the work being done on this volcano will be presented.

References. Devyatkin, E.V. and Smelov, S.B., 1979, Position of basalts in sequence of Cenozoic sediments of Mongolia: Izvestiya USSR Academy of Sciences, geological series, no. 1, p. 16-29. (In Russian).

Logatchev, N.A., Devyatkin, E.V., Malaeva, E.M., and others, 1982, Cenozoic deposits of Taryat basin and Chulutu river valley (Central Hangai): Izvestiya USSR Academy of Sciences, geological series, no. 8, p. 76-86. (In Russian).

Geologic Background. The Miocene Har-Togoo shield volcano, also known as Togoo Tologoy, is situated on top of a vast volcanic plateau. The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Information Contacts: Alexei V. Ivanov, Institute of the Earth Crust SB, Russian Academy of Sciences, Irkutsk, Russia; Bekhtur andM. Ulziibat, Research Center of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulan-Bator, Mongolia; M. Ganzorig, Institute of Informatics MAS, Ulan-Bator, Mongolia.


Elgon (Uganda) — December 2005

Elgon

Uganda

1.136°N, 34.559°E; summit elev. 3885 m

All times are local (unless otherwise noted)


False report of activity; confusion caused by burning dung in a lava tube

An eruption at Mount Elgon was mistakenly inferred when fumes escaped from this otherwise quiet volcano. The fumes were eventually traced to dung burning in a lava-tube cave. The cave is home to, or visited by, wildlife ranging from bats to elephants. Mt. Elgon (Ol Doinyo Ilgoon) is a stratovolcano on the SW margin of a 13 x 16 km caldera that straddles the Uganda-Kenya border 140 km NE of the N shore of Lake Victoria. No eruptions are known in the historical record or in the Holocene.

On 7 September 2004 the web site of the Kenyan newspaper The Daily Nation reported that villagers sighted and smelled noxious fumes from a cave on the flank of Mt. Elgon during August 2005. The villagers' concerns were taken quite seriously by both nations, to the extent that evacuation of nearby villages was considered.

The Daily Nation article added that shortly after the villagers' reports, Moses Masibo, Kenya's Western Province geology officer visited the cave, confirmed the villagers observations, and added that the temperature in the cave was 170°C. He recommended that nearby villagers move to safer locations. Masibo and Silas Simiyu of KenGens geothermal department collected ashes from the cave for testing.

Gerald Ernst reported on 19 September 2004 that he spoke with two local geologists involved with the Elgon crisis from the Geology Department of the University of Nairobi (Jiromo campus): Professor Nyambok and Zacharia Kuria (the former is a senior scientist who was unable to go in the field; the latter is a junior scientist who visited the site). According to Ernst their interpretation is that somebody set fire to bat guano in one of the caves. The fire was intense and probably explains the vigorous fuming, high temperatures, and suffocated animals. The event was also accompanied by emissions of gases with an ammonia odor. Ernst noted that this was not surprising considering the high nitrogen content of guano—ammonia is highly toxic and can also explain the animal deaths. The intense fumes initially caused substantial panic in the area.

It was Ernst's understanding that the authorities ordered evacuations while awaiting a report from local scientists, but that people returned before the report reached the authorities. The fire presumably prompted the response of local authorities who then urged the University geologists to analyze the situation. By the time geologists arrived, the fuming had ceased, or nearly so. The residue left by the fire and other observations led them to conclude that nothing remotely related to a volcanic eruption had occurred.

However, the incident emphasized the problem due to lack of a seismic station to monitor tectonic activity related to a local triple junction associated with the rift valley or volcanic seismicity. In response, one seismic station was moved from S Kenya to the area of Mt. Elgon so that local seismicity can be monitored in the future.

Information Contacts: Gerald Ernst, Univ. of Ghent, Krijgslaan 281/S8, B-9000, Belgium; Chris Newhall, USGS, Univ. of Washington, Dept. of Earth & Space Sciences, Box 351310, Seattle, WA 98195-1310, USA; The Daily Nation (URL: http://www.nationmedia.com/dailynation/); Uganda Tourist Board (URL: http://www.visituganda.com/).